Tom, I had the same problem on Fedora Core 3 (same error message when trying slightly older drivers than the 6629.) I've even recompiled a new kernel (currently using 2.6.10 latest stable from
http://kernel.org ) to to avail.
It was not until I used the 6629 drivers AND followed Carl Brunes post (
http://www.nvnews.net/vbulletin/show...t=40622&page=2 ) did things work. I highly suggest checking his post and trying that after explictly following these install instructions located at
http://www.mjmwired.net/resources/mj...3.shtml#nvidia , if your sure the drivers are installed properly, then try what Carl suggests.
After I followed the advice from mjmwired.net and THEN followed the advice from Carl, then and only then did everything work as expected.
I hope this helps.
ps. I can still produce the same error (though I have no need to use other drivers as the 6629's finally work. Thanks to mjmwired.net and Carl =)