Probably somebody/something botched a Fox runtime install. The error message you reported is usually caused by a version mismatch between vfp8renu.dll (or whatever your language is) and vfp8r.dll/vfp8t.dll. The dlls should show not only the same version number but also the same build (the internal revision id is not included in the version resource so you cannot check it from the outside).

You can force a specific resource dll to be loaded via the /L switch but it is better to repair the problem.