Two different crashes:

• First
  1. Install JBT 3.3.0.Beta2 from Marketplace on Juno milestone (skip WS for dependencies problems)
  2. After start and click on several menu items, there was a crash, see attached log hs_err_pid2460.log
• Second
  1. Just used JBT 4.0.0.Alpha1 for a while and then opened web page from jsf2 kickstart project. See log hs_err_pid2715.log. Hardly reproducible.

Logs analysis:

Log file	hs_err_pid2460.log	hs_err_pid2715.log
Eclipse version	Eclipse 4.2.M6 (for JavaEE developers)	Eclipse 4.2.0
JBoss Tools version	3.3.0.Beta2	4.0.0.A1
Java version	JRE 1.6.0_31-b04 64-bit	JRE 1.6.0_32-b05 64-bit
Linux version	Ubuntu SMP Fri Dec 2 64-bit (Ubuntu 12.04?)	Fedora release 17 64-bit
When reproduced?	While using JBoss Tools (without VPE?)	While starting VPE
Problematic frame	C [libmozjs.so+0x73830] unsigned+0xc20	C [ld-linux-x86-64.so.2+0x94eb]
Stack trace	Only Eclipse plugins in the stack trace	VPE and Eclipse plugins
Last call (the top of the stack)	XPCOM._JS_EvaluateUCScriptForPrincipals([BJJJ[CI[BI[J)I+0	XPCOM._Call(JJJJJI)I+0
Last call meaning (near the top of the stack)	Mozilla.onDispose()	Mozilla.initXPCOM()

Update:
This issue ([ld-linux-x86-64.so.2+0x94eb] part) should be fixed in Eclipse 4.2.1.

Workaround exists: remove libswt-xulrunner-fix.so from your swt plugin JAR and from your <user.home>/.mozilla/eclipse dir.