These are the most frustrating to figure out.
If you can get to the diagram without it crashing, start disabling bits of code (put it in a case structure so it won't run). See if you can narrow it down that way. Or make a copy of the app and start deleting sections of code. Sometimes getting rid of the offending code, then re-adding it will fix the problem.
You might try uninstalling and reinstalling NI-DAQ and any other driver sets you have installed one at a time. (reboot after each uninst and reinst) This might take care of it.
If none of that helps, your best bet will be to call NI support and see if they have any suggestions. But they'll probably tell you to uninstall everything related NI and reinstall if it's not a know problem
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I've been running LabVIEW 7 on XP almost since it was released and have had no real problems.
Good luck and let us know how it goes.
Ed

Ed Dickens - Certified LabVIEW Architect
Lockheed Martin Space
Using the Abort button to stop your VI is like using a tree to stop your car. It works, but there may be consequences.