I have a similar problem, along with other issues. I'm running XP Pro Service Pack 2, and In mission 2-1, I crash during briefing. All compatibility modes either crash in briefing, or crash when trying to load mechwarrior. In the first mission set, I ran into problems of vehicles bouncing up and down, and I found I had to hit them on the way down (easy enough, I like to shoot mechs while they're jumping). I also find that my pwn jets don't work, or only start to fly at the end of their fuel cycle.
So far, I've seen no fix anywhere for these issues. If I happen to stumble onto one, I'll post it here, but in the meantime, someone PLEASE give us some clues!!!!
