Hi MChartrand,
You mentioned that two other similar PCs work fine, is there a different HW/SW configuration on the PC that is not working. You may want to try looking at the following article:
How Can I Test My PC For Compatibility With LabVIEW Real-Time for Desktop ETS?
http://digital.ni.com/public.nsf/allkb/62538D52E61FC167862571C7006EDAC0
Here is another article that will help you verify if you have the correct HW:
Using a Desktop Computer as a LabVIEW Real-Time for ETS Target
http://zone.ni.com/devzone/cda/tut/p/id/4480
I hope this helps. Have a nice day!
Best regards,
Steven