This issue is related JBIDE-6450. When javax.xml.soap (1.3) bundle is loaded, it's unable to start WS Tester (java.xml.soap 1.2 can't be loaded properly). There is no problem on JBT 3.2.beta2, so it seems it's JBDS related (at least for some cases).

Error message:
Could not create the view: Plug-in "org.jboss.tools.ws.ui" was unable to instantiate class "org.jboss.tools.ws.ui.views.JAXRSWSTestView2".
java.lang.VerifyError: (class: org/jboss/tools/ws/ui/views/JAXRSWSTestView2, method: getOpNameFromRequestBody signature: ()Ljava/lang/String Incompatible object argument for function call
at java.lang.Class.getDeclaredConstructors0(Native Method)
at java.lang.Class.privateGetDeclaredConstructors(Class.java:2389)
at java.lang.Class.getConstructor0(Class.java:2699)
at java.lang.Class.newInstance0(Class.java:326)
at java.lang.Class.newInstance(Class.java:308)
at org.eclipse.core.internal.registry.osgi.RegistryStrategyOSGI.createExecutableExtension(RegistryStrategyOSGI.java:184)
at org.eclipse.core.internal.registry.ExtensionRegistry.createExecutableExtension(ExtensionRegistry.java:904)