When Mint was first installed did it behave like this or did the trouble start after an update or change in your hardware?
Ubuntu/Mint are both pretty good at detecting hardware on installation, but perhaps not so good at coping with some change. VESA works on any video card, by the way... if there is a "safe mode" you can boot into and select VESA, it might work. A fresh install (preserving your /home partition) is probably a certain cure. If it works you can set up (in both Ubuntu and Mint I believe) your Update Manager to accept only security updates afterwards, ignoring whatever updates might have b0rked your video display.
I know there's a recent update that ruined my own video settings in Xubuntu 10.04, literally putting my monitor to sleep at bootup! Grrrr.
I don't know if this has been helpful or not, but a fresh install ignoring all but security updates is what cured my video-crippled Xubuntu machine.
Hoping this helps,