extproc_connection_data test ORA-03113: end-of-file on communication channel

I'm trying to use an external DLL without any luck. When testing the extproc_connection_data service I get the following error.

What does this mean?

Initializing first test to use userid: scott, password: tiger Attempting to connect using userid: scott The test did not succeed.
ORA-03113: end-of-file on communication channel

There may be an error in the fields entered, or the server may not be ready for a connection.

Also, how can I find out what libraries have been created using create library 'C:\MyLibrary\MyDll.dll'

When I try to create one oracle says it created fine but then when trying to use a function I create that points to it I get an error "Invalid DLL Path" Received on Mon Apr 14 2003 - 14:22:14 CDT