Thank you so much!!! This has finally made it work.
It took some experimentation, but I've discovered I cannot make it work with agpgart at all. It only works if I have the NvAgp setting set to 1. This is fine by me though.
One more oddity I've noticed is that I can't seem to use any resolutions that match the aspect ratio of my laptop's native screen. (It's a 15.4" WSXGA+ screen). Resolutions like 1280x800 or 1680x1050 which work fine in Windows are rejected by the nvidia drivers. It's not a huge deal, as I can use resolutions like 1280x960 that result in only slight black bands on either side of the screen. Anyway, if anyone knows a way to make that work, excellent.
But in the meantime I'm just happy I can finally use my Linux boot again. Thanks so much Reeve and Moled!