USB is touchy sometimes. Try SD card or a network drive.
As recorded, played back on other system or OSD: Bad
Menus, even when recording is bad: Good
Video behind menus after the recording has gone bad:
? <- This will tell me if it has to do with the storage/recording process, or if the input is bad.
If you're on 3.33-2.00 or higher (including OSDng), the CF card is holding critical OS files. Removing it will cause the OSD to freeze / fail to boot.