Screen fades to white?

[S Freud]

I will try to explain this the best I can,

So recently my computer starting doing this weird thing, I will boot it up, it loads just fine but after being at the desktop for about a minute or two the screen just fades to white all of the sudden. It seems to freeze up and then the screen just starts fading in to white and I can't do anything, I booted in to safe mode and ran spybot and all of my anti virus stuff but came up with nothing.

Any ideas?

thanks