Comment 3 for bug 96954

Retrace done:
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#4 0xb7e21460 in pthread_mutex_lock () from /lib/tls/i686/cmov/libpthread.so.0
#5 0xad7ee858 in ?? () from /usr/lib/flashplugin-nonfree/libflashplayer.so
#6 0xac729024 in ?? ()
#7 0x01000000 in ?? ()
#8 0xb77f1256 in munmap () from /lib/tls/i686/cmov/libc.so.6
#9 0xadca012c in ?? () from /usr/lib/flashplugin-nonfree/libflashplayer.so
#10 0x00000000 in ?? ()
--- end of stack trace ---
...

Some third party addons found while retracing. Try to disable them and see if you can reproduce the crash. Extracted from apport error log:
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WARNING: library /usr/lib/flashplugin-nonfree/libflashplayer.so not found in system packages -- ignoring
WARNING: library /home/roger/.mozilla/firefox/i1sxvvsu.default/extensions/{3112ca9c-de6d-4884-a869-9855de68056c}/components/libgoogletoolbar.so not found in system packages -- ignoring
WARNING: library /usr/lib/Adobe/Acrobat7.0/Browser/intellinux/nppdf.so not found in system packages -- ignoring
WARNING: library /home/roger/.mozilla/firefox/i1sxvvsu.default/extensions/{3112ca9c-de6d-4884-a869-9855de68056c}/components/libmetrics.so not found in system packages -- ignoring
WARNING: dbgsym for libfreetype6 2.3.2-0mlind1 not found by glob "/tmp/ddebs/archives/libfreetype6-dbgsym_2.3.2-0mlind1_*.ddeb"
...

Tagging as mt-confirm for further processing