Ok, more facts: When I converted the report, I was logged into their T/S. I ran it from inside the Crystal application and got results. When I put it on the MAS menu and ran it from there, I got the message.
When I logged onto their server (not as me, but as Admin) and ran it from the MAS menu, I got data. Haven't had time to log into server as me and test - tomorrow's another day.