When using Visual Studio 2008 and debugging my unit tests... sometimes the debugger works fine. However very often after modifying some code then clicking \"Debug Unit Test\
One problem that I stumbled upon when trying to debug a test method was that it was private. Simply changing the method from private to public fixed my problem.
I don't know why this is a problem, but it probably has something to do with the implementation of the [Test] attribute of NUnit.