MacBookPro freezes completely when trying to connect to a projector

I have a brand new MacBookPro that I bought specifically to use to project movies, music, etc. Whenever I connect it to a projector with a VGA adapter cable, the projector cannot detect a signal. At first the computer screen will appear to recognize the display, but within seconds the computer freezes completely, to the point where I have to force it to shut down. Any ideas?