HELP! White/Blank Screen on start-up, but Comp fine

I was jus watching a movie on InterVideo WinDVD, then all of a sudden my Toshiba Satellite flashes White, the whole screen. But then i changed it to normal and not full screen and then it was fine.
BUT then i restarted the comp and on start-up the screen goes white then goes bac to normal and then does that a couple more times,
but my computer works fine, when i check everything.
also i plugged in another screen and that one doesnt turn white on start up so i think its the screen but i still dont no what it is.
HELP PLEASE!!!