I'm not familar with gitversion control, but I guess, there might be code in the master branch that didn't make it into the release. Moreover distros tend to include their own patches, so if your driver shipped with thed distro, there migth be small differences.
Too bad. I also made some further tests. I ran into the same problem using 32 bit linux and also with only 2gb ram in my machine.
(as I read that some drivers have problems with mem mapping when using 4gb on 64 bit, but that doesn't seem to be the isssue here)
Always got the corruption (unless I use the new driver and specify the small ram size using xorg 7.3).
Trying out fedora 9 with the new xorg wasn't better either.
So I don't have any idea what else to try.