Here's the error message from the log:
> Can't add that much data to backup set
> (limited to 1,000.0 G)
The problem here is that I'm only trying to archive 34 gigs! The discs have plenty of room and the AIT tape has plenty of room as well [which shouldn't matter anyway].
I have virtually two identical storage sets. One for backup and one for an archive safety copy with the delete option enabled. The backup set works fine, but all of a sudden the archive set is giving me this error. These sets have been in use for over a year - they span 15 tapes and contain 26 sessions and snapshots.
If I make a new storage set, the archive works normally. So I guess there's something wrong with the storage set itself. Recreating the set from tapes didn't solve anything. DAMMIT!!!