First if you havent already, try getting the lastest drivers for your vid card and installing them. If that doesnt work, try flashing the Bios on your Mobo. If that dont work, then Id try to run your gfx card at 4x agp,
and if none of that works, borrow a friends monitor and see if it still hapens. Also plz post ur system specs if you have a mobo with a km266 NB or a km400 that could be the problem, they are very very fininky with just about everything. post what kind of mobo you have also and the model # ill research it. one more thing, are you sure that your mobo can handle PC 2700? and if so can it take a gig of it? its like some nforce boards maybe they have three ram slots that can take pc-3200 but it cant take 3 gigs of it only two... it could be something like that.