Need help with Crimson Skies bug

OK, I'm playing the Crimson Skies single-player offline just fine. I go on Live; play a few games; download new content (Caverns and a plane); play more Live. But next time I went to continue the single-player campaign, it won't load it. It gets to the screen where it's supposed to show the current mission, but all it shows is the background image (the wide angle view of inside the zep hangar with two little worker guys hammering).

So did I somehow overwrite the saved campaign, run out of memory, wreck the hard drive or what?!?

zog