Arne,

VFP DLL's are dependent on several other support libraries (MSVCRT.DLL, MFC4x.DLL, etc). You should build your app with the distribution wizard to be sure these get copied to each machine. Of course some of your machine have these dependents, others don't. Check out the \Program Files\DevStudio\VFP\DISTRIB.SRC\SYSTEM for the collection of dependent files that VFPx.DLL need.

HTH,
Ed