Hello,
That looks like a very old indication of an internal LabVIEW error. The conditions you describe indicate it could be a memory leak - perhaps you are opening many references and not closing them somewhere in your code? Unfortunately, if the problem is in LabVIEW, and not the programming behind your application, I don't think R&D is going to be willing to consider fixing problems found in LabVIEW 5.1 - the product is now in version 8.0.
I hope it turns out to be in your code, and that you're able to fix it by removing a memory leak somewhere!
Best Regards,
JLS