When opening various popups in the Tridion Explorer, the message centre displays the message:
Couldn't retrieve data from 1 datasources
What does this mean, and how can I prevent it?
Edit: Yes - everyone who said UGC was right. In fact, the problem was not with referencing the web services, but that they weren't working correctly. So if you're setting up UGC, make sure you check (with your browser) that the OData services are not just available, but that they respond correctly to queries.