I had the same problem last week when YAM crashed several times. But it turned out that YAM was the victim, not the culprit, since there were bad blocks on the drive around the bitmap area. I managed to get all my files off the drive and scrap it for a new one.
I suggest you run Quarterback tools (or something else) on the drive to check for bad blocks (errant software can't cause them). If there are bad blocks, the disc is dying.
tony
