I've seen this error before with VIs that use tab controls created in 6.0 Studentor Eval version. LabVIEW 6.1, and 7.0 expecially, have much improved tab controls.
The VI might be corrupted. I was able to recover these VIs before by opening them in later version of LabVIEW and saving back with options for 6.0.
If you do not have a later LabVIEW version to use in this case, you can post your VI here and I will try to recover it in the above way for you.
Even better, email into support with your corrupted VI.
Zvezdana S.
National Instruments
