Following exception can be seen from log file occasionally when the system is at high load.

2011-02-01 00:52:14,845 ERROR [org.infinispan.interceptors.InvocationContextInterceptor] Execution error:
java.lang.ClassCastException: org.infinispan.container.entries.ImmortalCacheEntry cannot be cast to org.infinispan.container.entries.MVCCEntry
at org.infinispan.commands.write.ReplaceCommand.perform(ReplaceCommand.java:63)
at org.infinispan.interceptors.CallInterceptor.handleDefault(CallInterceptor.java:71)
at org.infinispan.commands.AbstractVisitor.visitReplaceCommand(AbstractVisitor.java:66)
at org.infinispan.commands.write.ReplaceCommand.acceptVisitor(ReplaceCommand.java:59)
at org.infinispan.interceptors.base.CommandInterceptor.invokeNextInterceptor(CommandInterceptor.java:118)
at org.infinispan.interceptors.DistributionInterceptor.handleWriteCommand(DistributionInterceptor.java:336)
at org.infinispan.interceptors.DistributionInterceptor.visitReplaceCommand(DistributionInterceptor.java:209)
at org.infinispan.commands.write.ReplaceCommand.acceptVisitor(ReplaceCommand.java:59)
at org.infinispan.interceptors.base.CommandInterceptor.invokeNextInterceptor(CommandInterceptor.java:118)
at org.infinispan.interceptors.LockingInterceptor.visitReplaceCommand(LockingInterceptor.java:338)
at org.infinispan.commands.write.ReplaceCommand.acceptVisitor(ReplaceCommand.java:59)
at org.infinispan.interceptors.base.CommandInterceptor.invokeNextInterceptor(CommandInterceptor.java:118)
at org.infinispan.interceptors.DeadlockDetectingInterceptor.handleDataCommand(DeadlockDetectingInterceptor.java:91)
at org.infinispan.interceptors.DeadlockDetectingInterceptor.visitReplaceCommand(DeadlockDetectingInterceptor.java:59)
at org.infinispan.commands.write.ReplaceCommand.acceptVisitor(ReplaceCommand.java:59)
at org.infinispan.interceptors.base.CommandInterceptor.invokeNextInterceptor(CommandInterceptor.java:118)
at org.infinispan.interceptors.base.CommandInterceptor.handleDefault(CommandInterceptor.java:132)
at org.infinispan.commands.AbstractVisitor.visitReplaceCommand(AbstractVisitor.java:66)
at org.infinispan.commands.write.ReplaceCommand.acceptVisitor(ReplaceCommand.java:59)
at org.infinispan.interceptors.base.CommandInterceptor.invokeNextInterceptor(CommandInterceptor.java:118)
at org.infinispan.interceptors.TxInterceptor.enlistWriteAndInvokeNext(TxInterceptor.java:184)
at org.infinispan.interceptors.TxInterceptor.visitReplaceCommand(TxInterceptor.java:142)
at org.infinispan.interceptors.DistTxInterceptor.visitReplaceCommand(DistTxInterceptor.java:90)
at org.infinispan.commands.write.ReplaceCommand.acceptVisitor(ReplaceCommand.java:59)
at org.infinispan.interceptors.base.CommandInterceptor.invokeNextInterceptor(CommandInterceptor.java:118)
at org.infinispan.interceptors.InvocationContextInterceptor.handleAll(InvocationContextInterceptor.java:87)
at org.infinispan.interceptors.InvocationContextInterceptor.handleDefault(InvocationContextInterceptor.java:58)
at org.infinispan.commands.AbstractVisitor.visitReplaceCommand(AbstractVisitor.java:66)
at org.infinispan.commands.write.ReplaceCommand.acceptVisitor(ReplaceCommand.java:59)
at org.infinispan.interceptors.InterceptorChain.invoke(InterceptorChain.java:273)
at org.infinispan.CacheDelegate.replace(CacheDelegate.java:475)
at org.infinispan.CacheSupport.replace(CacheSupport.java:96)
at net.beaumaris.common.persistence.cache.GenericInfinispanCache.replace(GenericInfinispanCache.java:339)
at net.beaumaris.dht.session.catv.service.impl.AccountIdToSessionIdCacheImpl.removeSessionFromAccount(AccountIdToSessionIdCacheImpl.java:72)
at net.beaumaris.dht.session.catv.service.impl.SessionCacheImpl.removeSessionFromAccount(SessionCacheImpl.java:111)
at net.beaumaris.dht.session.catv.service.impl.SessionCacheImpl.remove(SessionCacheImpl.java:77)
at net.beaumaris.dht.session.catv.service.impl.SessionCacheImpl.remove(SessionCacheImpl.java:45)
at net.beaumaris.dht.session.catv.facade.CATVSessionServiceFacade.delete(CATVSessionServiceFacade.java:153)
at sun.reflect.GeneratedMethodAccessor745.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at com.sun.jersey.server.impl.model.method.dispatch.AbstractResourceMethodDispatchProvider$VoidOutInvoker._dispatch(AbstractResourceMethodDispatchProvider.java:132)
at com.sun.jersey.server.impl.model.method.dispatch.ResourceJavaMethodDispatcher.dispatch(ResourceJavaMethodDispatcher.java:67)
at com.sun.jersey.server.impl.uri.rules.HttpMethodRule.accept(HttpMethodRule.java:259)
at com.sun.jersey.server.impl.uri.rules.RightHandPathRule.accept(RightHandPathRule.java:133)
at com.sun.jersey.server.impl.uri.rules.ResourceClassRule.accept(ResourceClassRule.java:83)
at com.sun.jersey.server.impl.uri.rules.RightHandPathRule.accept(RightHandPathRule.java:133)
at com.sun.jersey.server.impl.uri.rules.RootResourceClassesRule.accept(RootResourceClassesRule.java:71)
at com.sun.jersey.server.impl.application.WebApplicationImpl._handleRequest(WebApplicationImpl.java:990)
at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:941)
at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:932)
at com.sun.jersey.spi.container.servlet.WebComponent.service(WebComponent.java:384)
at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:451)
at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:632)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at net.beaumaris.common.servlet.TraceRequestResponseServletFilter.traceFilter(TraceRequestResponseServletFilter.java:195)
at net.beaumaris.common.servlet.TraceRequestResponseServletFilter.doFilter(TraceRequestResponseServletFilter.java:139)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:96)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:230)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
at org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(SecurityAssociationValve.java:182)
at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:84)
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:157)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:262)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:446)
at java.lang.Thread.run(Thread.java:619)

This happens occasionally.

The cache configuration:
<default>
<locking isolationLevel="READ_COMMITTED" lockAcquisitionTimeout="30000" useLockStriping="false"/>
<!--
This element specifies that the cache is clustered. modes supported:
distribution (d), replication (r) or invalidation . default is
local, non-clustered mode
-->
<clustering mode="d">
<l1 enabled="false" />
<hash numOwners="2"/>
<!--
Defines whether to retrieve state on startup
-->
<stateRetrieval timeout="3000" fetchInMemoryState="false" />
<sync replTimeout="3000" />
<!--
Uncomment this for async replication.
<async useReplQueue="true" replQueueInterval="10000" replQueueMaxElements="500" />
-->
</clustering>
<lazyDeserialization enabled="false"/>

<transaction useEagerLocking="false"
transactionManagerLookupClass="org.infinispan.transaction.lookup.GenericTransactionManagerLookup" />
<deadlockDetection enabled="true" spinDuration="1000" />
</default>
<namedCache name="session">
<clustering mode="d">
<l1 enabled="false"/>
<hash numOwners="2"/>
<sync/>
</clustering>
<transaction useEagerLocking="false" syncCommitPhase="false" syncRollbackPhase="false"
transactionManagerLookupClass="org.infinispan.transaction.lookup.DummyTransactionManagerLookup"/>
<indexing enabled="false" indexLocalOnly="false"/>
</namedCache>