Hi,
I'm getting the same thing, and I reported it as a bug in the code. (I think I over-reacted by calling it a high priority since there are at least 2 workarounds
Mine is putting an extra / in the destination file path as in:
Warning: rename(/home/mysite/moodledata/1/backupdata/backup-sa-c-mstevens-20041005-2027.zip,/home/mysite/moodledata/1//backup-sa-c-mstevens-20041005-2027.zip): No such file or directory in /home/mysite/www/moodle/files/index.php on line 220
Error: backup-sa-c-mstevens-20041005-2027.zip not moved