<p>Trying to establish a connection between my windows box (2003 server) and the oracle (11g) database.</p>

<p>I'm able to successfully ping the oracle host from the windows box. However tnsping command fails with the error tns-12532 error. </p>

<p>Any ideas to solve this issue?</p>

From
the Oracle Error Messages documentation
:
ORA-12532: TNS:invalid argument
Cause:
An internal function received an invalid parameter.
Action:
Not normally visible to the user. For further details, turn on tracing and reexecute the operation. If error persists, contact Oracle Customer Support.
Have you followed that path yet?