following error message occurred while backing up:

Error: Error occured, full traceback is bellow (gmb.py revision 691)
Traceback (most recent call last):
File "gmail-backup-gui.py", line 109, in _runThread
File "gmb.pyo", line 1232, in backup
File "gmb.pyo", line 963, in storeComplete
File "gmb.pyo", line 899, in _writeDownloadedIds
IOError: [Errno 2] No such file or directory: ...

can anybody help?