I was in the same boat as you. I wanted to use .NET/C# to run Selenium
Tests. I successfully run C# tests with NUnit against Selenium RC. I
then tried to run the tests in parallel using Selenium Grid and
switched to Gallio and MbUnit in order to do this (rather than Nunit
and PNunit). The tests did run in parrallel but with errors
(unexpected fails).
Regardless of selenium I learnt, incidentally, that Gallio/MbUnit is
superior to Nunit for testing.
I asked for help here
http://groups.google.com/group/selenium-users/browse_frm/thread/92b8a11534ef9a70
but got no reply.
I'm not clear that anyone has been successful running C# against
Selenium Grid in parallel. For the time being I've switched to writing
my tests in Java and TestNG. That seems to be the preferred/default
language that the Selenium Devs use and the Selenium Grid
documentation has Java examples.
I'm in the process of creating my own hello world Java and Selenium
Grid example and I'm more optimistic of success using that platform.