There's sizeof(int) verses sizeof(void*) problem in Firefox's autocomplete implementation that causes frequent crashes anytime you're typing in autocomplete-enabled input boxes on a 64bit platform. Upstream has it fixed, but it's not in 0.9.3. Here's the patch.
Created attachment 103614 [details] fix frequent crashes on 64bit platforms
upstream, for comparison: http://lxr.mozilla.org/seamonkey/source/toolkit/components/satchel/src/nsFormHistory.cpp#781
Is this fixed in our 0.10 (PR) firefox package?
AFAICT, your 0.10 (PR) package isn't available to the public. However, if it's based on firefox-1.0PR-source.tar.bz2, then, yes, it's fixed.
Should be in rawhide soon.