Re: Login Error...

Hare's what will get you started on an NT: Check that your TNS<sid>Listener [Control Panel --> Services --> ] is running.

Also, isn't the error a TNS-12650 ?
TNS-12560 TNS:protocol adapter error

Cause: A generic protocol adapter error occurred.

Action: Check addresses used for proper protocol specification. Before reporting this error, look at the error stack and check for lower level transport errors.For further details, turn on tracing and re-execute the operation. Turn off tracing when the operation is complete.

HTH, Mark

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