Comment 31 for bug 401055

After uninstalling Swfdec and put proprietary Flash 10 plugin, it works well, but it needs last version of Flash 10, I read that old version, in addition to a security risk, could also cause this crash.

http://labs.adobe.com/downloads/flashplayer10.html

Download the tar.gz file.

Go to .Mozilla in your home and create a new folder "plugins".
Extract libflashplayer.so inside and restart Firefox.

I hope it can help.