Are you sure you're calling the right webservice? What soap endpoint are you trying to reach? The modeler doesn't "know" where it's running so the WSDL always publishes http://localhost:8080/ as the url. If you want to run it on another server or run multiple versions on the same machine, you have to change the hostname and/or port in Project | Settings | Server | Application root URL
Project2 (sending partner) reports: "com.mendix.systemwideinterfaces.MendixRuntimeException: Received SOAP fault, code: AuthenticationError, reason: Login failed"
Project1 (receiving end) reports: "Login FAILED: invalid password for user 'xxx'", where 'xxx' stands for the correct webservice user name.
Now the error in Project1 doesn't leave room for interpretation. But I can assure you that the password hardcoded in the ws-call matches exactly with the user's master record.
Both projects run on the same machine - one at port 8080, the other on 8081.