hi have you changed any settings on your comp lately?
also what os are you running, vista or xp.
you can try changing your display settings to see will this fix the problem although if it is a constant problem as you say there may be something further affecting it.
go to control panel and select your display settings, i only have vista to hand at the moment so the screen may appear different on xp, change your screen resolution to see will these changes solve your problem. come back to us if you have no joy :)
give your make and model of laptop being used if you can :)
cheers ive tried doin certain settings like u have described just tried diff things not sure i done it right tho. mine is vista also and make is fujitsu siemans it stopped flashin before then a week later started doin it again before was he worst it would flash so much then like coulours would come up and screen go all white.
best go get it fixed with the warranty so rather than opening it up, save everything, then demand a new laptop!, tell there could be too many problems with it to just replace the screen, motherboard issues and so on, if they say anything send em here an we'll sort them out! lol