I was working on a silverlight application that was connecting to an ADO.Net dataservice on my server. All of a sudden I started getting following error.
Request Error: The server encountered an error processing the request. See server logs for more details
I looked at event logs and sql server logs. I could not find anything wrong in the logs. Then I started thinking back to figure out what did I change in service that may have caused anything to break. Only thing I remember changing was that sql connection was changed from windows authentication to sql authentication. I looked at connection string and everything looked fine there as well. I tested the credentials and they were fine. After banging my head for few minutes I tried couple of URL in service and nothing worked. I fired up SQL profiler and started monitoring the requests. I did not see a single query making into it from ADO.Net data service. I looked at connection string again and there you go. There was typo. Instead of "User ID" I had typed "UserID" to provide login name. After I fixed that, everything worked like a charm.
You can see that error message from data service was not very helpful. So every time you run into this obscure error, make sure that you check names in query strings etc. to make sure there are no typos.