It looks like the Windows version on Vista Home Premium is stripping the first character of the year during the restore. For example, the folder structure of the backup is 2009\12\email.eml well the restore is trying to read 009\12\email.eml and the file doesn't exist. See the traceback below. NOTE: I've changed my account address.

GMail Backup revision 664 (2008-12-03)
Restoring the content of account curtis@xxx.com from D:\Users\Curt\Documents\Gmail Backup 2\
Error: Error occured while reading e-mail from disc
Ignoring this error message.
If you want, please report the following traceback at www.gmail-backup.com/forum
Thanks! (gmb.py revision 664):
Traceback (most recent call last):
File "gmb.pyo", line 804, in iterBackups
IOError: [Errno 2] No such file or directory: u'D:\\Users\\Curt\\Documents\\Gmail Backup 2\\000\\01\\20000112-152159-orders@act-labs.com-Your_ACT_LABS_Order_Confirmation_for_ORDER_#137128-1.eml'

End of restoring of account curtis@xxx.com
You are using the latest version of GMail Backup.