Hav You tried checking the filesystem on this disk?
Second thing would be that all the downloaded data wasn't flushed on to the disk before the crash.

Looks like some sort of a memory leak, i never had a problem with such one using Deluge. It stays at about 60MB together (both deluge and deluged). But Azureus without a memory leak takes about 300 MB minimum

400kB torrent, what is it when compared to 30GB of data
Making bigger pieces makes a greater chance to lose it due to data corruption (always happens).