I'm having the same issue since upgrading to firefox-3.5. Karmic x86_64 with the same versions of firefox-3.5 and xulrunner-1.9.1 but with swfdec-mozilla (0.8.2-1ubuntu1) instead of flashplugin. As mentioned above, "firefox --sync" makes it harder to trigger the crash.
I'm having the same issue since upgrading to firefox-3.5. Karmic x86_64 with the same versions of firefox-3.5 and xulrunner-1.9.1 but with swfdec-mozilla (0.8.2-1ubuntu1) instead of flashplugin. As mentioned above, "firefox --sync" makes it harder to trigger the crash.