Update
The plot thickens...
I used "Manage Snapshots..." and found that it's the most recent snapshot that has the I/O error. I tried creating a new snapshot, and Parallels gives an error: "Operation failed. An error occurred while reading the disk. Problem ID 21029. The corresponding KB article says "Parallels Desktop failed to perform an operation due to errors on the Mac hard disk." and has instructions for repairing the disk using the Apple Disk Utility.
Before I try Disk Utility, I decided to revert to an earlier snapshot. But I get the same error from Parallels when I use Manage Snapshots to revert to an earlier snapshot. This makes me wonder how effective the snapshot facility is! If I have a corrupt VM, but the corruption prevents me from switching to an earlier snapshot, what have I gained by using snapshots?
UPDATE:
I called AppleCare, and they believe it's a simple case of a corrupt file, not a failing hard drive. Apple recommends that I delete the specific file that has the issue. I suspect that would cause issues with Parallels, so that sounds like a Bad Idea.
I thought I might be able to replace it with a Time Machine backup, but I realize that I would have to replace the entire Windows 7.pvm file because Time Machine won't let me replace individual files that are inside that package.
My preference would be to use Parallels Manage Snapshots to get rid of the bad snapshot, but that gives the I/O error.
Anyone have ideas?
Thanks!
Last edited: May 26, 2012