Doing backup I obatain the following error

GMail Backup revision 653 (2008-10-15)
Starting backup of account alessandro.*****@gmail.com into /Users/*****/Work/Backups/gmail-backup-20090703
Error: Error occured, full traceback is bellow (gmb.py revision 653)
Traceback (most recent call last):
File "/Users/******/Software/GmailBackup/gmail-backup-0.104-linux/svc/scripting/__init__.py", line 348, in run
retval = self.main(**objects)
File "/Users/****/Software/GmailBackup/gmail-backup-0.104-linux/svc/scripting/__init__.py", line 1396, in main
self.invokeCommand(c)
File "/Users/*****/Software/GmailBackup/gmail-backup-0.104-linux/svc/scripting/__init__.py", line 1416, in invokeCommand
return method(**method_kwargs)
File "gmail-backup.py", line 158, in backup
File "gmb.py", line 906, in backup
File "gmb.py", line 515, in connect
File "/opt/local/Library/Frameworks/Python.framework/Versions/2.5/lib/python2.5/imaplib.py", line 1128, in __init__
IMAP4.__init__(self, host, port)
File "/opt/local/Library/Frameworks/Python.framework/Versions/2.5/lib/python2.5/imaplib.py", line 163, in __init__
self.open(host, port)
File "gmb.py", line 343, in open
File "/opt/local/Library/Frameworks/Python.framework/Versions/2.5/lib/python2.5/imaplib.py", line 1141, in open
self.sslobj = socket.ssl(self.sock, self.keyfile, self.certfile)
AttributeError: 'module' object has no attribute 'ssl'

Any suggestion?
Best regards