Comment 6 for bug 14911

You may add the following line in your firefox starting script (/usr/bin/firefox):

export XLIB_SKIP_ARGB_VISUALS=1

It solve my problems too.

(In reply to comment #5)
> I had this same problem occur. In my case, it was due to the flash player
> trying to play sounds and being unable to. I modified
> /etc/mozilla-firefox/mozilla-firefoxrc and changed FIREFOX_DSP from "auto" to
> "none". Since doing this, everything seems to work great. I did not verify if
> this happened in other plugins that use sound or not.