>>Post the piece from .NET that calls this function and exact code of the function. Sometimes there are things overlooked, that the fresh eye can catch in a glimpse.
>
>If the call from .NET would not work, my test code that manipulates the TEST.DBF would not work either. I think it is something on the VFP side.

Have you tried to hard code the path in the SP? Have you tried to write and fire the code in your .NET form without the SP?