[Samba] Winbind failed

[blizzards at libero.it]

Hello all.
I'm trying to investigate a problem that occur every days and force me to 
restart samba.
I'm using samba 3.5.6 (last stable) è winbind joining windows ads.
Every day, at unpredictable time, the logs show me:

Jan 17 08:24:53 xxx winbindd[13585]:   Kinit failed: Preauthentication failed 
Jan 17 08:24:53 xxx winbindd[13584]: [2011/01/17 08:24:53.550079,  0] 
libsmb/cliconnect.c:1052(cli_session_setup_spnego) 
Jan 17 08:24:53 xxx winbindd[13584]:   Kinit failed: Preauthentication failed 

So i need to restart samba in order to let authentication restart normally.
I have upgraded for 3.0.36 (this version had no problem at all).

Someone can help me to solve that?