Ron - One thing I've noticed in the AMA Motocross series is none of the riders are using the waterproof case on their helmet mounted cameras. I'm guessing that's to improve audio performance though I haven't tried using the frame mount yet:
http://shop.gopro.com/mounts/the-fra....html#/start=1
The skeleton case helps to some degree but I still think the only way to get halfway decent audio is utilizing a remote mic interior mounted.
You also might try performing another firmware upgrade as a form of reboot. I doubt the camera corrupts itself but........?