This hackintosh of mine is a trip. When logged in as an ordinary user I ask Leopard to use a video mode not of its choosing. The screen turns blue and fails to revert back to the previous setting. Perhaps if I had an Apple LCD display it would behave differently but I doubt it. I rebooted the machine from an ssh login and tried to login as the same user who had the blue screen. Guess what? I login and the screen turns blue and stays that way.
Anyway to expunge the broken setting all you need do is ssh into the stricken user's account and:
Lemme know if this works for you.