This bug was filed from the Socorro interface and is report bp-f80a855f-3639-4545-a631-9146c2140906. ============================================================= Steps: -play youtube video - switch between videos( same page/tab) Frame Module Signature Source 0 XUL js::jit::RangeAnalysis::truncate() obj-firefox/x86_64/dist/include/mozilla/Vector.h 1 XUL js::jit::OptimizeMIR(js::jit::MIRGenerator*) js/src/jit/Ion.cpp 2 XUL js::jit::CompileBackEnd(js::jit::MIRGenerator*) js/src/jit/Ion.cpp 3 XUL js::HelperThread::handleIonWorkload() js/src/vm/HelperThreads.cpp 4 XUL js::HelperThread::threadLoop() js/src/vm/HelperThreads.cpp 5 libnss3.dylib _pt_root nsprpub/pr/src/pthreads/ptthread.c Ø 6 libsystem_pthread.dylib libsystem_pthread.dylib@0x1898 Ø 7 libsystem_pthread.dylib libsystem_pthread.dylib@0x1729 Ø 8 libsystem_pthread.dylib libsystem_pthread.dylib@0x5fc8 9 libnss3.dylib libnss3.dylib@0x20467f

Seems to be a dupe of bug 1062612 - please reopen if it still happens with builds that have the fix.