It's a new crash signature that first appeared in 13.0a1/2012020 on Windows and 13.0a1/20120219 on Mac OS X. The regression range is: http://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=550779e6bab4&tochange=4d47329bb02e The likely culprit is bug 641025. Signature js::GCMarker::processMarkStackTop(js::SliceBudget&) More Reports Search UUID 6b7ef8a1-52f6-46ca-b5a8-f909d2120224 Date Processed 2012-02-24 10:15:45 Uptime 34 Last Crash 11.7 weeks before submission Install Age 1.6 days since version was first installed. Install Time 2012-02-22 20:04:34 Product Firefox Version 13.0a1 Build ID 20120222031223 Release Channel nightly OS Windows NT OS Version 6.1.7601 Service Pack 1 Build Architecture x86 Build Architecture Info GenuineIntel family 6 model 42 stepping 7 Crash Reason EXCEPTION_ACCESS_VIOLATION_READ Crash Address 0x7c4fd7e0 App Notes AdapterVendorID: 0x1002, AdapterDeviceID: 0x9498, AdapterSubsysID: 22691787, AdapterDriverVersion: 8.632.1.2000 D3D10 Layers? D3D10 Layers- D3D9 Layers? D3D9 Layers- EMCheckCompatibility True Total Virtual Memory 2147352576 Available Virtual Memory 1768087552 System Memory Use Percentage 54 Available Page File 2731278336 Available Physical Memory 960667648 Frame Module Signature [Expand] Source 0 mozjs.dll js::GCMarker::processMarkStackTop js/src/jsgcmark.cpp:1069 1 mozjs.dll js::GCMarker::drainMarkStack js/src/jsgcmark.cpp:1154 2 mozjs.dll IncrementalGCSlice js/src/jsgc.cpp:3481 3 mozjs.dll AutoCopyFreeListToArenas::AutoCopyFreeListToArenas js/src/jsgc.cpp:3431 4 mozjs.dll GCCycle js/src/jsgc.cpp:3620 5 nspr4.dll PR_EnterMonitor nsprpub/pr/src/threads/prmon.c:99 6 mozjs.dll Collect js/src/jsgc.cpp:3683 7 xul.dll nsDOMUIEvent::Release content/events/src/nsDOMTransitionEvent.cpp:76 8 mozjs.dll js::GCSlice js/src/jsgc.cpp:3709 9 mozjs.dll js::IncrementalGC js/src/jsfriendapi.cpp:156 10 xul.dll nsXPConnect::Collect js/xpconnect/src/nsXPConnect.cpp:426 11 KERNELBASE.dll ReleaseSemaphore More reports at: https://crash-stats.mozilla.com/report/list?signature=js%3A%3AGCMarker%3A%3AprocessMarkStackTop%28js%3A%3ASliceBudget%26%29 https://crash-stats.mozilla.com/report/list?signature=js%3A%3AGCMarker%3A%3AprocessMarkStackTop

Can we combine this with bug 719114? All that happened was that the function got a new parameter. It's possible that the crash rate when up a little, but it's really hard to tell with so little data.