Error message with backup at 13% Gmail French

I use gmail french version

I have tested with account test (50 emails) Gmail-backup work perfectly.

BUT with my firt account on Gmail, I can't backup my emails, backup stop à 13%

error message :

Error: Error occured, full traceback is bellow ( revision 674)
Traceback (most recent call last):
File "", line 109, in _runThread
File "gmb.pyo", line 1235, in backup
File "gmb.pyo", line 427, in handleError
File "gmb.pyo", line 420, in nExceptionMsg
UnicodeDecodeError: 'ascii' codec can't decode byte 0xe9 in position 265: ordinal not in range(128)