Well, if you're trying to use an old RGB monitor like the one for the IIGS it won't work, it has less pins even though the connector is the same. I'm not sure why a VGA monitor won't work as long as you have the right adapter though. I have the beige g3 tower I just picked up connected to a 14" Apple color plus display using on board video with no problems. Maybe something got jarred loose when you took the card out. Try reseating any cards, ram etc and see if that helps.