I have the same problem and I realized the cause of this is that I chose the virtual drive to be set up on a partition which I formatted in the FAT32 file system instead of the MAC OS X system. I thought it was the right thing to do and it turned out to be wrong.
After retrying a few times of setting up the virtual drive on the partition with the FAT32 file system with the drive corrupting for no reason, I reformatted the partition to native Mac OS X file system and set up the virtual drive on it again, the drive has not corrupted for even once since.
This requirement is actually briefly mentioned in the user guide of Parallel Desktop, but I personally missed out on it.
Sorry for the run-on sentences, but anyhow, hope this helps.
Miss Joey
Last edited: Apr 25, 2007