You mention that MediaLab just goespurple when it attempts to launch a DirectRT session. I am aware of this issuewith the 2010.3 version and have a fix I can offer for it:

http://support.empirisoft.com/showthread.php?t=532
(scroll down toward the end of the thread)

But I think youmention that DirectRT also does not run studies when using ONLY DirectRT--is thatcorrect? If so, what happens when you try?