Proxies throw "IllegalStateException: Type parameter must be a concrete type" when running a lot of clients concurrently

This exception arises when running around 7+ clients.

Stacktrace:
java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
at org.jboss.ejb3.interceptors.container.AbstractContainer.invokeCallback(AbstractContainer.java:262)
at org.jboss.ejb3.EJBContainer.invokeCallback(EJBContainer.java:1300)
at org.jboss.ejb3.EJBContainer.invokePostConstruct(EJBContainer.java:1311)
at org.jboss.ejb3.stateful.StatefulContainer.create(StatefulContainer.java:157)
at org.jboss.ejb3.cache.simple.SimpleStatefulCache.create(SimpleStatefulCache.java:402)
at org.jboss.ejb3.stateful.StatefulContainer.createSession(StatefulContainer.java:408)
at org.jboss.ejb3.session.SessionContainer.createSession(SessionContainer.java:676)
at org.jboss.ejb3.proxy.impl.factory.session.stateful.StatefulSessionProxyFactoryBase.getNewSessionId(StatefulSessionProxyFactoryBase.java:227)
at org.jboss.ejb3.proxy.impl.factory.session.stateful.StatefulSessionProxyFactoryBase.createProxyBusiness(StatefulSessionProxyFactoryBase.java:140)
at org.jboss.ejb3.proxy.impl.objectfactory.session.SessionProxyObjectFactory.createProxy(SessionProxyObjectFactory.java:129)
at org.jboss.ejb3.proxy.impl.objectfactory.session.stateful.StatefulSessionProxyObjectFactory.getProxy(StatefulSessionProxyObjectFactory.java:64)
at org.jboss.ejb3.proxy.impl.objectfactory.ProxyObjectFactory.getObjectInstance(ProxyObjectFactory.java:161)
at javax.naming.spi.NamingManager.getObjectInstance(NamingManager.java:304)
at org.jnp.interfaces.NamingContext.getObjectInstance(NamingContext.java:1483)
at org.jnp.interfaces.NamingContext.getObjectInstanceWrapFailure(NamingContext.java:1500)
at org.jnp.interfaces.NamingContext.lookup(NamingContext.java:824)
at org.jnp.interfaces.NamingContext.lookup(NamingContext.java:688)
at javax.naming.InitialContext.lookup(InitialContext.java:392)
at org.jboss.weld.integration.ejb.JBossSessionObjectReference.<init>(JBossSessionObjectReference.java:44)
at org.jboss.weld.integration.ejb.JBossEjbServices.resolveEjb(JBossEjbServices.java:68)
at org.jboss.weld.bean.SessionBean.createReference(SessionBean.java:450)
at org.jboss.weld.bean.proxy.EnterpriseBeanProxyMethodHandler.<init>(EnterpriseBeanProxyMethodHandler.java:76)
at org.jboss.weld.bean.SessionBean.create(SessionBean.java:326)
at org.jboss.weld.context.DependentContext.get(DependentContext.java:62)
at org.jboss.weld.manager.BeanManagerImpl.getReference(BeanManagerImpl.java:660)
at org.jboss.weld.bean.AbstractReceiverBean.getReceiver(AbstractReceiverBean.java:83)
at org.jboss.weld.bean.ProducerMethod$1.produce(ProducerMethod.java:141)
at org.jboss.weld.bean.AbstractProducerBean.create(AbstractProducerBean.java:360)
at org.jboss.weld.context.DependentContext.get(DependentContext.java:62)
at org.jboss.weld.manager.BeanManagerImpl.getReference(BeanManagerImpl.java:660)
at org.jboss.weld.el.AbstractWeldELResolver$1.call(AbstractWeldELResolver.java:125)
at org.jboss.weld.el.ELCreationalContext.putIfAbsent(ELCreationalContext.java:63)
at org.jboss.weld.el.AbstractWeldELResolver.getValue(AbstractWeldELResolver.java:120)
at org.jboss.weld.integration.webtier.jsf.ForwardingELResolver.getValue(ForwardingELResolver.java:51)
at javax.el.CompositeELResolver.getValue(CompositeELResolver.java:175)
at com.sun.faces.el.FacesCompositeELResolver.getValue(FacesCompositeELResolver.java:72)
at org.apache.el.parser.AstIdentifier.getValue(AstIdentifier.java:67)
at org.apache.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:187)
at org.jboss.weld.el.WeldValueExpression.getValue(WeldValueExpression.java:71)
at org.jboss.weld.el.WeldValueExpression.getValue(WeldValueExpression.java:71)
at com.sun.faces.facelets.el.TagValueExpression.getValue(TagValueExpression.java:102)
at com.sun.faces.facelets.component.UIRepeat.getValue(UIRepeat.java:265)
at com.sun.faces.facelets.component.UIRepeat.getDataModel(UIRepeat.java:241)
at com.sun.faces.facelets.component.UIRepeat.setIndex(UIRepeat.java:431)
at com.sun.faces.facelets.component.UIRepeat.process(UIRepeat.java:465)
at com.sun.faces.facelets.component.UIRepeat.encodeChildren(UIRepeat.java:926)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1613)
at javax.faces.render.Renderer.encodeChildren(Renderer.java:168)
at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:848)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1613)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1616)
at com.sun.faces.application.view.FaceletViewHandlingStrategy.renderView(FaceletViewHandlingStrategy.java:380)
at com.sun.faces.application.view.MultiViewHandler.renderView(MultiViewHandler.java:126)
at javax.faces.application.ViewHandlerWrapper.renderView(ViewHandlerWrapper.java:273)
at com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:127)
at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
at com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:139)
at javax.faces.webapp.FacesServlet.service(FacesServlet.java:313)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:324)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:242)
at org.tuckey.web.filters.urlrewrite.RuleChain.handleRewrite(RuleChain.java:164)
at org.tuckey.web.filters.urlrewrite.RuleChain.doRules(RuleChain.java:141)
at org.tuckey.web.filters.urlrewrite.UrlRewriter.processRequest(UrlRewriter.java:90)
at org.tuckey.web.filters.urlrewrite.UrlRewriteFilter.doFilter(UrlRewriteFilter.java:417)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:274)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:242)
at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:734)
at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:541)
at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:479)
at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:407)
at org.tuckey.web.filters.urlrewrite.NormalRewrittenUrl.doRewrite(NormalRewrittenUrl.java:195)
at org.tuckey.web.filters.urlrewrite.RuleChain.handleRewrite(RuleChain.java:159)
at org.tuckey.web.filters.urlrewrite.RuleChain.doRules(RuleChain.java:141)
at org.tuckey.web.filters.urlrewrite.UrlRewriter.processRequest(UrlRewriter.java:90)
at org.tuckey.web.filters.urlrewrite.UrlRewriteFilter.doFilter(UrlRewriteFilter.java:417)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:274)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:242)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:275)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(SecurityAssociationValve.java:181)
at org.jboss.modcluster.catalina.CatalinaContext$RequestListenerValve.event(CatalinaContext.java:285)
at org.jboss.modcluster.catalina.CatalinaContext$RequestListenerValve.invoke(CatalinaContext.java:261)
at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:88)
at org.jboss.web.tomcat.security.SecurityContextEstablishmentValve.invoke(SecurityContextEstablishmentValve.java:100)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.jboss.web.tomcat.service.jca.CachedConnectionValve.invoke(CachedConnectionValve.java:158)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.jboss.web.tomcat.service.request.ActiveRequestResponseCacheValve.invoke(ActiveRequestResponseCacheValve.java:53)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:362)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:877)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:653)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:951)
at java.lang.Thread.run(Thread.java:619)
Caused by: java.lang.reflect.InvocationTargetException
at sun.reflect.GeneratedMethodAccessor309.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.jboss.ejb3.interceptors.aop.LifecycleCallbackInterceptorMethodLazyInterceptor.invoke(LifecycleCallbackInterceptorMethodLazyInterceptor.java:109)
at org.jboss.aop.joinpoint.ConstructionInvocation.invokeNext(ConstructionInvocation.java:80)
at org.jboss.ejb3.core.context.CurrentInvocationContextInterceptor.invoke(CurrentInvocationContextInterceptor.java:47)
at org.jboss.aop.joinpoint.ConstructionInvocation.invokeNext(ConstructionInvocation.java:80)
at org.jboss.ejb3.interceptors.aop.InvocationContextInterceptor.setup(InvocationContextInterceptor.java:88)
at org.jboss.aop.advice.org.jboss.ejb3.interceptors.aop.InvocationContextInterceptor_z_setup_599089570.invoke(InvocationContextInterceptor_z_setup_599089570.java)
at org.jboss.aop.joinpoint.ConstructionInvocation.invokeNext(ConstructionInvocation.java:80)
at org.jboss.aspects.currentinvocation.CurrentInvocationInterceptor.invoke(CurrentInvocationInterceptor.java:67)
at org.jboss.aop.joinpoint.ConstructionInvocation.invokeNext(ConstructionInvocation.java:80)
at org.jboss.ejb3.interceptors.container.AbstractContainer.invokeCallback(AbstractContainer.java:258)
... 93 more
Caused by: org.jboss.weld.exceptions.IllegalStateException: WELD-000023 Type parameter must be a concrete type: [field] @Inject private org.jboss.weld.examples.pastecode.session.CodeFragmentManagerImpl.hashComputer
at org.jboss.weld.bean.builtin.AbstractFacade.getFacadeType(AbstractFacade.java:52)
at org.jboss.weld.event.EventImpl.of(EventImpl.java:59)
at org.jboss.weld.bean.builtin.EventBean.newInstance(EventBean.java:74)
at org.jboss.weld.bean.builtin.EventBean.newInstance(EventBean.java:34)
at org.jboss.weld.bean.builtin.AbstractFacadeBean.create(AbstractFacadeBean.java:46)
at org.jboss.weld.context.DependentContext.get(DependentContext.java:62)
at org.jboss.weld.manager.BeanManagerImpl.getReference(BeanManagerImpl.java:660)
at org.jboss.weld.manager.BeanManagerImpl.getReference(BeanManagerImpl.java:734)
at org.jboss.weld.manager.BeanManagerImpl.getInjectableReference(BeanManagerImpl.java:757)
at org.jboss.weld.injection.FieldInjectionPoint.inject(FieldInjectionPoint.java:118)
at org.jboss.weld.util.Beans.injectBoundFields(Beans.java:840)
at org.jboss.weld.util.Beans.injectFieldsAndInitializers(Beans.java:852)
at org.jboss.weld.bean.SessionBean$1$1.proceed(SessionBean.java:187)
at org.jboss.weld.injection.InjectionContextImpl.run(InjectionContextImpl.java:54)
at org.jboss.weld.bean.SessionBean$1.inject(SessionBean.java:182)
at org.jboss.weld.integration.ejb.SessionBeanInterceptor.postConstruct(SessionBeanInterceptor.java:98)
... 106 more

This exception can be seen here in hudson job: http://hudson.qa.jboss.com/hudson/view/Weld/job/perf-weld-pastecode-stress-single/74/console-qa05/