Unable to delete recording

I have an HR20-700, with a 1 TB external drive. I've had a season pass for Voyager to record all eipsodes, for several months. Last week, somehow an episode was recorded that shows a length of 49 hours, 28 mins. [Edit: Figured out how. When I came home from a weekend away, the DVR was locked up with the record light still on. It must have locked up while recording, and shomehow "thought" it was recording that whole time.] I am unable to delete this recording - I've tried the red key, dash dash, and selecting "delete" from the menu. Inevitably, the DVR locks up. (I've let it sit for hours, it never recovers.)

I have tons of recordings, and about 40 season passes -- I do NOT want to delete everything and start over!! Help!?!