Have a look for the error in the application's log (tersus.log) - there might be additional details following it which will shed light on the issue.
Also, please clear up the following:
Is the model a client side one? I.e. Get Server URL & Prepare Request executing on the client, with Service To connect server executed on the server? If so, note that the <URL> trigger (if that's what the top one on Service To connect server is), is interpreted by the platform to mean the url through which Service To connect server is called (as explained in http://www.tersus.com/#Id=5585 - see Strategy 2). If you're using Strategy 1, then you should name the trigger something else. It's generally a good idea to refrain altogether from using the <> characters to surround user-defined element names, in order to avoid such unexpected behavior.
For best results, use the Firefox browser..