I have the exact same problem as Tori. When trying to run an input file, I receive a message saying that "There is another instance of executeDRT.exe still running", although there are no other active tasks. My task manager shows that the executeDRT.exe file is not responding. This happened on multiple computers. Closing the program, restarting the computer - nothing helps.
I am using DirectRT, not MediaLab, and the file is relatively short and simple. Just yesterday it worked ok, and now the program is not responding.
Sample input files don't run either.