I have the same problem. Settings file has all my previous configs from the beta, however it is still only detecting 1024x768. Video card is a Geforce 240 and Drivers are up to date within the last week or 2. Verifying the game data with steam did not seem to do anything as well, and changing the settings to a .bak did not have any effect, and no other file has taken its place.
After a bit of digging I do believe I have found the problem, or at least a way around it. The files are getting put into the "My Documents/my games" folder instead of what was normally "appdata/local/" folder. Least I believe that's the case, as the settings match up for what it's showing in game.
EDIT: After changing the settings file to say 1600x1200, all resolutions are now being displayed.