Created attachment 503145 [details]
backtrace

Description of problem:

Firefox crashed and won't restart.  I get a segfault everytime I try to start it.

Version-Release number of selected component (if applicable):
firefox-4.0.1-2.fc15.x86_64

How reproducible:
always

Steps to Reproduce:
1. firefox
2. firefox --debug
3.
  
Actual results:

The crash dialog box comes up.  Clicking restart brings up another crash dialog, etc.

Expected results:

Firefox should start up.

Additional info:

Partial backtrace (see full backtrace in attachment)

Program received signal SIGSEGV, Segmentation fault.
__pthread_mutex_lock (mutex=0x0) at pthread_mutex_lock.c:51
51        unsigned int type = PTHREAD_MUTEX_TYPE (mutex);

Thread 1 (Thread 0x7ffff7fd2740 (LWP 15133)):
#0  __pthread_mutex_lock (mutex=0x0) at pthread_mutex_lock.c:51
#1  0x0000003a16c22df9 in PR_Lock (lock=0x0) at ../../../mozilla/nsprpub/pr/src/pthreads/ptsynch.c:206
#2  0x0000003a130b6eb8 in AutoLockGC (rt=0x8dd660, this=<synthetic pointer>) at jscntxt.h:2601
#3  js::GCHelperThread::finish (this=0x8dd8d8, rt=<optimized out>) at jsgc.cpp:2048
#4  0x0000003a130b7044 in js_FinishGC (rt=0x8dd660) at jsgc.cpp:869
#5  0x0000003a13049ec1 in JSRuntime::~JSRuntime (this=0x8dd660, __in_chrg=<optimized out>) at jsapi.cpp:707
#6  0x0000003a13049fc9 in JS_Finish (rt=0x8dd660) at jsapi.cpp:774
#7  0x0000003a1304a03a in JS_Init (maxbytes=33554432) at jsapi.cpp:764
#8  0x0000003a1d9a191a in XPCJSRuntime::XPCJSRuntime (this=0x8daa50, aXPConnect=<optimized out>) at xpcjsruntime.cpp:1355
#9  0x0000003a1d9a2290 in XPCJSRuntime::newXPCJSRuntime (aXPConnect=0x8da9a0) at xpcjsruntime.cpp:1417
#10 0x0000003a1d98e752 in nsXPConnect::nsXPConnect (this=<optimized out>) at nsXPConnect.cpp:106
#11 0x0000003a1d98e7bb in nsXPConnect::GetXPConnect () at nsXPConnect.cpp:167
#12 0x0000003a1d601014 in nsContentUtils::Init () at nsContentUtils.cpp:441
#13 0x0000003a1d4a4a09 in nsLayoutStatics::Initialize () at nsLayoutStatics.cpp:164
#14 0x0000003a1d4a3887 in Initialize () at nsLayoutModule.cpp:402