Does anyone know why Load tests kill subsequent Test Runner Debug sessions?

During the course of the day I will run Load Tests to a Web API. If I see repeated errors, I stop the load test prematurely and then attempt to run the test via Test Runner (to Debug the Test). No dice, I have to reboot VS2013 to get Test Runner to respond! The compile phase works fine but Test Runner doesn't appear to do anything... Just wondering if anyone else has seen this issue and what to do to stop it.