Ah, I think I understand. You set up a pre-login trigger, but the DLL doesn't exist, so any login attempt is blocked? Interesting situation - I hadn't thought of this case before.
One thing you can do, if you remember the name of the DLL and function, is compile a trigger that registers that function, and the function just returns zero. Then, put the DLL in place and log in.
Or, you should be able to eliminate the trigger by connecting to Oracle and updating the proper tables, assuming you have access to the data server. Contact PTC's tech support for this - they should be able to step you through the process.