Have you tried MPLAB 8.2? Versions 6 and 7 are pretty badly antiquated. You could be struggling with an old and now fixed problem.
If you want, post a sample of what you are trying and I'll try it here, let you know result.
I have downloaded MPLAB 8.3 and started using it. Even in this version, same problem persists. I think, there may be an inherent problem in MPLAB in this regard. However, if you can find any solution, please let me know.