Whenever i try to run my own map and sometimes the supplied maps, a blank grey screen shows up and everything stops, is there a way to fix this? and whats wrong with it.

(It seems that it works sometimes if i let the intro play and load another map before i try my custom one)

Please help me with this problem.

can you just hear the sounds?, if so check here

no, what happens is all of the backgorund sounds stop after the screen goes blank, its as if the level loaded, but the game isn't playing it.

Try turning off the intro. It causes a lot of problems on many PC's it seems.