Try going on a map and just putting this in the console:
loadMission("base/data/missions/planetcave.mis");
If that crashes, we know its not a problem with the trigger. If it does crash, its a trigger problem and we'll come to that later.
So if it does crash, try doing:
loadMission("base/data/missions/bedroom.mis");
If it doesn't crash, you've got a problem with your planetcave.mis file, if it continues to crash, Try on a new install. If it stops crashing, you borked your BL.