Thanks for this information. Seeing that you are using version 2006 on a computer running Windows 8.1 makes me curious if you would still see this error when using DirectRT ver 2012.4.164; you can find it at http://www.empirisoft.com/Download.aspx?index=4. I would suggest that you save whatever DirectRT files you have somewhere besides your computer, install a trial copy of DirectRT 2012.3.164, and see if your input files and some of the Samples folder files run without seeing the Overflow error.