A little more information would probably help here:
What software are you using (LabVIEW, CVI, C++...) and what version?
What are you doing in your program? Are you building unbounded arrays (In LabVIEW, this would be something like a build array in a loop) ?
What is your system like, i.e. RAM, etc.
Are you using any NI hardware? If so, what?
-Alan A.