Clear all Winbind caches and flush Net cache, always take a backup before deleting 😉
Stop the Winbind service and Samba service (if you have it):
root# service winbind stop
root# service smb stop
Clear the Samba Net cache:
root# net cache flush
Delete the Winbind caches:
root# rm –f /var/lib/samba/*.tdb
root# rm –f /var/lib/samba/group_mapping.ldb
Start the Samba (if you have it) and then Winbind services
root# service smb start
root# service winbind start