I hit the following fatal assertion while browsing, causing my browser to crash: Assertion failure: mDocument->IsXUL() || mDocument->GetReadyStateEnum() == nsIDocument::READYSTATE_INTERACTIVE || (mDocument->GetReadyStateEnum() == nsIDocument::READYSTATE_UNINITIALIZED && NS_IsAboutBlank(mDocument->GetDocumentURI())) (Bad readystate), at /home/dbaron/builds/ssd/mozilla-central/mozilla/layout/base/nsDocumentViewer.cpp:1017 When I hit the assertion, I was looking at the links to flights I've taken at the bottom of http://dbaron.org/about -- I was clicking some of the links and going back repeatedly. (What was saved in my sessionstore after the assertion was that the tab had the 2011 flights loaded.) (gdb) bt 8 #0 0x00007fd8001c103d in nanosleep () at ../sysdeps/unix/syscall-template.S:82 #1 0x00007fd8001c0edc in __sleep (seconds=0) at ../sysdeps/unix/sysv/linux/sleep.c:138 #2 0x00007fd7fbc9c1bc in ah_crap_handler (signum=11) at /home/dbaron/builds/ssd/mozilla-central/mozilla/toolkit/xre/nsSigHandlers.cpp:89 #3 0x00007fd7fbca88db in nsProfileLock::FatalSignalHandler (signo=11, info=0x7fff73525c30, context=0x7fff73525b00) at /home/dbaron/builds/ssd/mozilla-central/obj/firefox-debugopt/toolkit/profile/nsProfileLock.cpp:190 #4 <signal handler called> #5 0x00007fd7fc0092f9 in DocumentViewerImpl::LoadComplete (this=0x12971840, aStatus=<optimized out>) at /home/dbaron/builds/ssd/mozilla-central/mozilla/layout/base/nsDocumentViewer.cpp:1009 #6 0x00007fd7fcffa77b in nsDocShell::EndPageLoad (this=0x3db86450, aChannel= 0x47d99748, aStatus=0, aProgress=<optimized out>) at /home/dbaron/builds/ssd/mozilla-central/mozilla/docshell/base/nsDocShell.cpp:6422 #7 0x00007fd7fcffcb07 in nsDocShell::OnStateChange (this=0x3db86450, aProgress=0x3db86478, aRequest=0x47d99748, aStateFlags=<optimized out>, aStatus=0) at /home/dbaron/builds/ssd/mozilla-central/mozilla/docshell/base/nsDocShell.cpp:6253 (More stack frames follow...) (gdb) f 5 #5 0x00007fd7fc0092f9 in DocumentViewerImpl::LoadComplete (this=0x12971840, aStatus=<optimized out>) at /home/dbaron/builds/ssd/mozilla-central/mozilla/layout/base/nsDocumentViewer.cpp:1009 warning: Source file is more recent than executable. 1009 MOZ_ASSERT(mDocument->IsXUL() || // readyState for XUL is bogus (gdb) l 1004 nsIDocShell *docShell = window->GetDocShell(); 1005 NS_ENSURE_TRUE(docShell, NS_ERROR_UNEXPECTED); 1006 1007 docShell->GetRestoringDocument(&restoring); 1008 if (!restoring) { 1009 MOZ_ASSERT(mDocument->IsXUL() || // readyState for XUL is bogus 1010 mDocument->GetReadyStateEnum() == 1011 nsIDocument::READYSTATE_INTERACTIVE || 1012 // test_stricttransportsecurity.html has old-style 1013 // docshell-generated about:blank docs reach this code! (gdb) l 1014 (mDocument->GetReadyStateEnum() == 1015 nsIDocument::READYSTATE_UNINITIALIZED && 1016 NS_IsAboutBlank(mDocument->GetDocumentURI())), 1017 "Bad readystate"); 1018 mDocument->SetReadyStateInternal(nsIDocument::READYSTATE_COMPLETE); 1019 1020 nsRefPtr<nsDOMNavigationTiming> timing(mDocument->GetNavigationTiming()); 1021 if (timing) { 1022 timing->NotifyLoadEventStart(); 1023 } (gdb) p mDocument $1 = { mRawPtr = 0x426957e0 } (gdb) p $1.mRawPtr $2 = (nsHTMLDocument *) 0x426957e0 (gdb) p $2->GetReadyStateEnum() $3 = nsIDocument::READYSTATE_COMPLETE (gdb) p mDocument->mDocumentURI $4 = { mRawPtr = 0x11e1a690 } (gdb) p $.mRawPtr $5 = (nsStandardURL *) 0x11e1a690 (gdb) p $->mSpec $6 = { <nsACString_internal> = { mData = 0x3c548448 "http://dbaron.org/about", mLength = 23, mFlags = 5 }, <No data fields>} This assertion was introduced relatively recently in https://hg.mozilla.org/mozilla-central/rev/fa6a84e7ba53

Oops, looks like this might be a duplicate of bug 779959.