Hey cheetahman,
Have you tried the obvious so far, putting your 256 back in it's slot? altough normally it will beep at you if it has problems booting with the new stick.
The slots are not normally located near the screen connections, is it possible the laptop could have been banged, or too much pressure put on the back of the screen when the
RAM was being installed? The screen itself is extremely delicate, with only a thin layer of plasic covering it. Very easy to damage.
If you wait for the laptop to bootup normally (if it still does), wait for your HDD light to stop flashing. You may have your usual welcome to windows sound theme. If you look closely at the screen in a dark room, can you just about make out part of your desktop or welcome page very faintly?