I have gotten the error massage while backup on 691 version.

Please explain about this massage so that I can understand what is wrong.

Error: Error while saving e-mail
Ignoring this error message.
If you want, please report the following traceback at www.gmail-backup.com/forum
Thanks! (gmb.py revision 691):
Traceback (most recent call last):
File "gmb.pyo", line 1225, in backup
File "gmb.pyo", line 956, in store
IOError: [Errno 13] Permission denied:

Thanks in advance.