"The last two times, the download stopped at around 2.9 GB and 2.3 GB respectively, each time claiming some problem on the harddrive, and suggesting that I might be running the torrent twice (which I wasn't). "

Just that part (none of the other parts). I tried Azureus (the first time) and it reached 99% completion (an improvement) and crashed (illegal operation). So I reloaded Azureus and it no longer shows as downloading (hopefully it finished). I think the problem is the BiT Torrent Client (not exactly sure) but hopefully it'll work. I'll check the MD5 checksum on it and see if it gives any errors. Thanks.