I don't know why you are experiencing this kind of problem, but the best solution is:
- First, exit the game.
- Delete "settings.dat" which is located in your "My Documents/NBA Live 08/settings" folder.
- Then, get into the game and try to adjust settings.
- Then go to "Load/Save" and save settings again.
If you have that problem with your dynasty settings, you can just put new-generated(the settings you have saved recently) "settings.dat" into your "My Documents/NBA Live 08/Saves/(Dynasty save name)".
Btw, i can even run the game with 640*480 resolution. So, i don't think there's a big problem and the best solution is above.
Good luck