Be more specific. When does it crash? What unit did you mod? How did you mod it?
Here are a few crash conditions, in case one of them fits what you did.
--If you tried giving something an air attack that doesn't usually have one, you'll need to give it an air attack script in ICE or ICECC.
--If you made vision >= 12 then Starcraft will just crash
--If you tried to make units other than Zerglings or Scourge hatch from one egg, you'll need to give them the birth script "Zergling Birth" or, I think, "Scourge Birth".