I'm running ATI 2010 (5,055) on Vista 64 Home Premium. I set up a weekly backup to copy my critical documents to my ISP via FTP. It ran to completion with no complaints - the first time.
The second time (and this might be a coincidence), I got the above error on three files before I canceled the backup. The files it complained about all seem to be accessible through Explorer.
I'm attaching the ATI log.