When you say you d/l the driver from the website and it works fine and dandy and works like it should what do you mean? Can you change the resolution? And then when it converts over to the generic driver you resolution is not set properly?
When you go into Device Manager is there a yellow

beside display adapter? If there is no

then the deivce is working properly.
Have you removed the device physically then re-seat it?
If Windows detects a problem with the video card or video driver, it restarts with the VGA driver.
Heres a link on how to install or change a video driver.
I'd say if your computer keeps losing the driver the card is on its way out. The only other thing would be a faulty monitor.
Hope this helps