error with Serial port.. permission issue?

[pur]

I'm trying to connect to a forwarded serial port ( RDP / TS session ) but i get the error "invalid function".

The application that is trying to open up the port, is written in .Net version 2 using the serialport class, but i also tried opening it with hyperterminal, also without succes.

After failing to do it with the RDP session i start testing on the local machine but this also gives me no connection.

Now i don't know for sure that the permissions are set correctly for the account, if anyone could point me out to some documention or could tell me where i could find those settings , so that i could rule that out , would be nice.

Or better , if someone knows the real cause of an "invalid function" error.