How to solve this problem?
I have this ProjectName.UnitTests.config file, and I did exactly what the documentation said: http://nant.sourceforge.net/release/latest/h
Find this thread on Sourceforge's nant-users mailing list. I would provide the same advice Erich Eichinger gives:
I recommend avoiding the nunit2 task at all and simply switch to <exec> nunit-console [...]
<exec>
Additionally you get some extra goodness with NUnit 2.5.