I've followed your instructions but am still stuck in a resolution of 1280x1024. I didn't receive any error messages when going through the instructions either. Any ideas? I have the MSI GTX 260 (nVidia). I have a second card in the system too, the nVidia 9800GT but it's not actually connected to a monitor. It's in for PhysX on the Windows side of my system.

UPDATE: Ultimately I had to do a clean install of SL. Everything went perfectly until I use the Migration Assistant. Some setting from the old system transferred over and messed up the new install. So, had to re-install and manually install all my software again. No biggie though considering everything now works.