Comment 2 for bug 348614

This seems to be the same as bug #338892.

In the other bug, the developer said:
"did this go away in the meantime?
either its a out of memory issue or you didnt restart your browser after upgrade i would think."

Just taking a note for myself ;-) : some say running firefox as root could cure similar bugs, and that the prefs.js file was taken by root in ~/mozilla. Would be sad to loose bug because it is fix so simply however.