Hey!!! I found an answer to this one, by chance. I noticed that when I copied a 60gb file, it would report that it was only about 10% of the way done, when it actually had copied 30gb of it, and that it would copy about 55gb, and then die with either no error message, or "file copy error". So I fired the original VM back up (it seemed to work just fine), and scheduled a CHKDSK for the next boot. Ran the CHKDSK, rebooted, then shut down the guest, and started the copy over, and voila!!!
IT WORKED! :-)