Here is the result of running Firefox 3.5.3 with Firebug 1.5b1 enabled, under gdb:

Starting program: /usr/lib/firefox-3.5.3/firefox 
[Thread debugging using libthread_db enabled]
[New Thread 0x7fffe6bf0910 (LWP 28721)]
[New Thread 0x7fffe61e5910 (LWP 28722)]
[New Thread 0x7fffe53ff910 (LWP 28723)]
[New Thread 0x7fffe40c5910 (LWP 28724)]
[Thread 0x7fffe40c5910 (LWP 28724) exited]
[New Thread 0x7fffe40c5910 (LWP 28725)]
[New Thread 0x7fffe36ff910 (LWP 28726)]
[Thread 0x7fffe40c5910 (LWP 28725) exited]
[New Thread 0x7fffe40c5910 (LWP 28727)]
[New Thread 0x7fffde0b9910 (LWP 28739)]
[New Thread 0x7fffdd8b8910 (LWP 28740)]
[Thread 0x7fffe36ff910 (LWP 28726) exited]

Program received signal SIGSEGV, Segmentation fault.
js_PCToLineNumber (cx=0x7fffdc921400, script=0x7ffff66281c0, pc=0xf66282c9 <Address 0xf66282c9 out of bounds>) at jsscript.cpp:1808
1808	jsscript.cpp: No such file or directory.
	in jsscript.cpp
Current language:  auto
The current source language is "auto; currently c++".
(gdb) bt
#0  js_PCToLineNumber (cx=0x7fffdc921400, script=0x7ffff66281c0, pc=0xf66282c9 <Address 0xf66282c9 out of bounds>) at jsscript.cpp:1808
#1  0x00007ffff53a3594 in jsd_GetClosestLine (jsdc=0x7fffdcff0680, jsdscript=0x7fffdc839be0, pc=4133651145) at jsd_scpt.c:523
#2  0x00007ffff53a96cd in jsds_FilterHook (jsdc=0x7fffdcff0680, state=<value optimized out>) at jsd_xpc.cpp:400
#3  0x00007ffff53aa2f3 in jsds_ExecutionHookProc (jsdc=0x7fffdcff0680, jsdthreadstate=0x7fffdc838a40, type=4, callerdata=<value optimized out>, 
    rval=0x7fffffff7298) at jsd_xpc.cpp:680
#4  0x00007ffff53a26ef in jsd_CallExecutionHook (jsdc=0x7fffdcff0680, cx=<value optimized out>, type=4133651145, 
    hook=0x7ffff53aa1c4 <jsds_ExecutionHookProc>, hookData=0x0, rval=<value optimized out>) at jsd_hook.c:177
#5  0x00007ffff63831f9 in js_Interpret (cx=0x7fffe49ea800) at jsinterp.cpp:7227
#6  0x00007ffff638f34d in js_Invoke (cx=0x7fffe49ea800, argc=<value optimized out>, vp=0x7fffe46651a0, flags=<value optimized out>) at jsinterp.cpp:1394
#7  0x00007ffff638f6a4 in js_InternalInvoke (cx=0x7fffe49ea800, obj=0x7fffe49c9400, fval=140737028854912, flags=0, argc=1, argv=<value optimized out>, 
    rval=0x7fffffff75d0) at jsinterp.cpp:1447
#8  0x00007ffff6357836 in JS_CallFunctionValue (cx=0x7fffdc921400, obj=0x7ffff66281c0, fval=4133651145, argc=<value optimized out>, 
    argv=<value optimized out>, rval=<value optimized out>) at jsapi.cpp:5187
#9  0x00007ffff4d3e841 in nsXPCWrappedJSClass::CallQueryInterfaceOnJSObject (this=<value optimized out>, ccx=..., jsobj=0x7fffe49c9400, 
    aIID=<value optimized out>) at xpcwrappedjsclass.cpp:294
#10 0x00007ffff4d3ef10 in nsXPCWrappedJSClass::DelegatedQueryInterface (this=0x7fffe6e910c0, self=0x7fffe54a5d30, aIID=..., aInstancePtr=0x7fffffff77d8)
    at xpcwrappedjsclass.cpp:819
#11 0x00007ffff54c4312 in nsCOMPtr_base::assign_from_qi (this=0x7fffffff7910, qi=..., iid=...) at nsCOMPtr.cpp:96
#12 0x00007ffff4d43723 in nsCOMPtr<nsIClassInfo>::operator= (ccx=..., Object=<value optimized out>, Scope=0x7fffe6ec3180, Interface=0x7fffdc951380, 
    cache=0x0, isGlobal=<value optimized out>, resultWrapper=0x7fffffff7a10) at ../../../../dist/include/xpcom/nsCOMPtr.h:658
#13 XPCWrappedNative::GetNewOrUsed (ccx=..., Object=<value optimized out>, Scope=0x7fffe6ec3180, Interface=0x7fffdc951380, cache=0x0, 
    isGlobal=<value optimized out>, resultWrapper=0x7fffffff7a10) at xpcwrappednative.cpp:378
#14 0x00007ffff4d2e7c5 in XPCConvert::NativeInterface2JSObject (ccx=..., d=<value optimized out>, dest=0x7fffffff7c20, src=0x7fffdc85ef00, 
    iid=<value optimized out>, Interface=<value optimized out>, cache=0x0, scope=0x7fffdc862200, allowNativeWrapper=0, isGlobal=0, pErr=0x7fffffff7aac)
    at xpcconvert.cpp:1146
#15 0x00007ffff4d22c06 in nsXPConnect::WrapNativeToJSVal (this=<value optimized out>, aJSContext=<value optimized out>, aScope=0x7fffdc862200, 
    aCOMObj=0x7fffdc85ef00, aIID=0x7ffff66e5548, aVal=0x7fffffff7c08, aHolder=0x7fffffff7c20) at nsXPConnect.cpp:1258
#16 0x00007ffff4d20c21 in nsXPConnect::WrapNative (this=0x7fffdc921400, aJSContext=0x7ffff66281c0, aScope=0xf66282c9, aCOMObj=0x7ffff65fb3e0, aIID=..., 
    aHolder=<value optimized out>) at nsXPConnect.cpp:1234
#17 0x00007ffff4d33c28 in nsJSCID::GetService (this=0x7fffdc964dd0, _retval=<value optimized out>) at xpcjsid.cpp:898
#18 0x00007ffff54fda71 in NS_InvokeByIndex_P (that=0x7fffdc921400, methodIndex=4133650880, paramCount=4133651145, params=0x7ffff65fb3e0)
    at xptcinvoke_x86_64_linux.cpp:208
#19 0x00007ffff4d411fd in XPCWrappedNative::CallMethod (ccx=..., mode=<value optimized out>) at xpcwrappednative.cpp:2454
#20 0x00007ffff4d48c73 in XPC_WN_CallMethod (cx=0x7fffe49ea800, obj=<value optimized out>, argc=<value optimized out>, argv=<value optimized out>, 
    vp=<value optimized out>) at xpcwrappednativejsops.cpp:1590
#21 0x00007ffff638f343 in js_Invoke (cx=0x7fffe49ea800, argc=<value optimized out>, vp=0x7fffe4665170, flags=<value optimized out>) at jsinterp.cpp:1386
#22 0x00007ffff638057c in js_Interpret (cx=0x7fffe49ea800) at jsinterp.cpp:5179
#23 0x00007ffff638f34d in js_Invoke (cx=0x7fffe49ea800, argc=<value optimized out>, vp=0x7fffe4665038, flags=<value optimized out>) at jsinterp.cpp:1394
#24 0x00007ffff4d3d978 in nsXPCWrappedJSClass::CallMethod (this=0x7fffe4ae7480, wrapper=<value optimized out>, methodIndex=<value optimized out>, 
    info=0x7fffe4711060, nativeParams=0x7fffffff8ce0) at xpcwrappedjsclass.cpp:1697
#25 0x00007ffff54fe651 in PrepareAndDispatch (self=0x7fffe465d620, methodIndex=<value optimized out>, args=0x7fffffff8e60, gpregs=0x7fffffff8de0, 
    fpregs=0x7fffffff8e10) at xptcstubs_x86_64_linux.cpp:151
#26 0x00007ffff54fdb13 in SharedStub () from /usr/lib/xulrunner-1.9.1.3/libxul.so
#27 0x00007ffff5017ec0 in nsEventListenerManager::HandleEventSubType (this=<value optimized out>, aListenerStruct=0x7fffdffdc008, aListener=0x7fffe465d620, 
    aDOMEvent=0x7fffdc964d80, aCurrentTarget=0x7fffe49ea478, aPhaseFlags=28718) at nsEventListenerManager.cpp:1098
#28 0x00007ffff5018261 in nsEventListenerManager::HandleEvent (this=<value optimized out>, aPresContext=<value optimized out>, aEvent=0x7fffffff9260, 
    aDOMEvent=0x7fffffff91d0, aCurrentTarget=<value optimized out>, aFlags=<value optimized out>, aEventStatus=0x7fffffff91d8)
    at nsEventListenerManager.cpp:1206
#29 0x00007ffff503142a in nsEventTargetChainItem::HandleEvent (this=0x7fffdc864038, aVisitor=..., aFlags=6, aMayHaveNewListenerManagers=-459360136)
    at nsEventDispatcher.cpp:236
#30 0x00007ffff503155f in nsEventTargetChainItem::HandleEventTargetChain (this=<value optimized out>, aVisitor=..., aFlags=6, aCallback=0x0, 
    aMayHaveNewListenerManagers=1) at nsEventDispatcher.cpp:300
#31 0x00007ffff5031a1e in nsEventDispatcher::Dispatch (aTarget=<value optimized out>, aPresContext=<value optimized out>, aEvent=0x7fffffff9260, 
    aDOMEvent=0x0, aEventStatus=0x7fffffff92a8, aCallback=<value optimized out>) at nsEventDispatcher.cpp:514
#32 0x00007ffff4e93eb6 in DocumentViewerImpl::LoadComplete (this=0x7fffe481b220, aStatus=2152988680) at nsDocumentViewer.cpp:1006
#33 0x00007ffff52bfe12 in nsDocShell::EndPageLoad (this=0x7fffe49e9800, aProgress=<value optimized out>, aChannel=0x7ffff673de00, aStatus=2152988680)
    at nsDocShell.cpp:5365
#34 0x00007ffff52c16d9 in nsWebShell::EndPageLoad (this=0x7fffe49e9800, aProgress=0x7fffe49e9828, channel=0x7ffff673de00, aStatus=2152988680)
    at nsWebShell.cpp:1013
#35 0x00007ffff52b9a7f in nsDocShell::OnStateChange (this=0x7fffe49e9800, aProgress=0x7fffe49e9828, aRequest=0x7ffff673de00, 
    aStateFlags=<value optimized out>, aStatus=2152988680) at nsDocShell.cpp:5261
#36 0x00007ffff52cb655 in nsDocLoader::FireOnStateChange (this=0x7fffe49e9800, aProgress=0x7fffe49e9828, aRequest=<value optimized out>, 
    aStateFlags=131088, aStatus=<value optimized out>) at nsDocLoader.cpp:1259
#37 0x00007ffff52cb758 in nsDocLoader::doStopDocumentLoad (this=0x7fffdc921400, request=0x7ffff673de00, aStatus=2152988680) at nsDocLoader.cpp:880
#38 0x00007ffff52cc463 in nsDocLoader::DocLoaderIsEmpty (this=0x7fffe49e9800, aFlushLayout=<value optimized out>) at nsDocLoader.cpp:785
#39 0x00007ffff52cc628 in nsDocLoader::OnStopRequest (this=0x7fffe49e9800, aRequest=0x7fffe496d830, aCtxt=<value optimized out>, aStatus=0)
    at nsDocLoader.cpp:680
#40 0x00007ffff4d83f69 in nsLoadGroup::RemoveRequest (this=0x7fffe4a48ec0, request=0x7fffe496d830, ctxt=0x0, aStatus=0) at nsLoadGroup.cpp:688
#41 0x00007ffff4fc627e in nsDocument::DoUnblockOnload (this=0x7fffe4a60800) at nsDocument.cpp:7107
#42 0x00007ffff50d8593 in nsBindingManager::DoProcessAttachedQueue (this=0x7fffe4793e80) at nsBindingManager.cpp:978
#43 0x00007ffff50d9911 in nsRunnableMethod<nsBindingManager>::Run (this=<value optimized out>) at ../../../dist/include/xpcom/nsThreadUtils.h:264
#44 0x00007ffff54f2e37 in nsThread::ProcessNextEvent (this=0x7ffff6738700, mayWait=1, result=0x7fffffff99bc) at nsThread.cpp:510
#45 0x00007ffff54c85db in NS_ProcessNextEvent_P (thread=0x7fffdc921400, mayWait=-161316416) at nsThreadUtils.cpp:227
#46 0x00007ffff544c3fd in nsBaseAppShell::Run (this=0x7fffeaa36e20) at nsBaseAppShell.cpp:170
#47 0x00007ffff53234d0 in nsAppStartup::Run (this=0x7fffeaa94480) at nsAppStartup.cpp:193
#48 0x00007ffff4d18f5f in XRE_main (argc=<value optimized out>, argv=<value optimized out>, aAppData=<value optimized out>) at nsAppRunner.cpp:3347
#49 0x000000000040271f in ?? ()
#50 0x00007ffff6be3abd in __libc_start_main () from /lib/libc.so.6
#51 0x0000000000401f99 in ?? ()
#52 0x00007fffffffe3b8 in ?? ()
#53 0x000000000000001c in ?? ()
#54 0x0000000000000001 in ?? ()
#55 0x00007fffffffe666 in ?? ()
#56 0x0000000000000000 in ?? ()