I was using ReSharper's Unit Test Runner today, and all was good until it suddenly stopped working with no error message.  You would run the tests, it would spin for a second, then show no results - everything was grey.  Try to run test in debug mode, same thing, no break points ever get hit.

This was very frustrating since I had no indication of what the problem was.  I ended up throwing the test DLL into NUnit itself, which showed a nice error dialog "Assembly Not Loaded" which indicated there was an error in the test project's app.config.  Argh!

At least it gave me an excuse to download and install NUnit 2.4.7.  Apparently they added rowtest support?  I like the sound of that.