Kao što verovatno već znaš, Username i Password moraju biti ukucani identično onako kako su i definisani na serveru.
Najjednostavniji način koji ja znam da bi korisnicima omogućio da ukucaju latinicu i onda kada im je tastatura podešena na ćirilicu jeste da na login prozoru forsiraš promenu keyboard layouta na English. Ima Windows API funkcija koja upravo to radi. Pogledaj malo MSDN.
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