i wouldnt recommend it, but have you tried smacking the area by the buttons? that might could fix it. probably just a bad button, just a question, whats the model number of it?
probably something simple like a button going out. when the osd pops up what does it do on the osd. does it do nothing or does it scroll around? is there a menu button or can u press any button on it? and alother question. did u touch the monitor any time before the osd popped back up?