Hi,
I get the same error message. I'm running DirectRT version 2008.1 (NOT the beta upgrade) on Windows 7 computers. I am attaching my input file as well. I created and ran this study on Windows XP computers with DirectRT version 2006 and did not have any problems.
One other note is that after clicking "OK" and acknowledging the error message, I get to the first screen (blank black screen) of the DirectRT file, but can't go any further. I have to force-quit the program and when I do so, the resolution for the monitors is messed up and set to the lowest setting.
Please advise.