Moze da bude milion stvari. Najcesce je disablovan TCP/IP na SQL serveru ili zatvoren port. Proveri "SQL Server configuration manager" (start->programs ->sqlserver XXX-> tamo_negde ), izaberi "SQL Server network configuration" i proveri da li je TCP/IP enabled, ako jeste proveri binding na javni IP i port, port 1311 mi se cini cudan.
if it walks like a duck and quacks like a duck, it could be a dragon doing a duck
impersonation.