We've just created a new public forum for answering ICorDebug and MDbg questions. Check out:
   http://forums.microsoft.com/MSDN/ShowForum.aspx?ForumID=868&SiteID=1

This is a great place to post any questions you have about the Mdbg sample, ICorDebug, the CLR debugging services, etc. If you're writing your own managed debugger, or just writing a simple tool on top of ICorDebug/MDbg, you definitely want to keep this forum in mind.