So you cannot get your DirectRT files to run in DirectRT at all on some of you machines? Could you please be a bit more clear as to exactly what the error is? And do you have the exact wording of any error or message boxes from the machines that don't work?

Also, is the attached dxdiag report for the machines that do or don't work? And is it different from the other kind of machines (does vs. don't run your DirectRT files)?