Well to be perfectly honest with you, I've just installed Fedora yesterday after a long Windows XP stint. (The wife got mad at me changing distros every month.
So I just got her her own computer.)
But I too have an X300 so I would definitely blame it on our card. The little time that I did play around with it yesterday, it crashed twice while in Firefox. Meaning, the screen froze up completely, causing me to have to cold reboot.
I haven't looked at the driver situation yet.