The error code 0xBFFF009E (your error code is actually negative) basically means "library not found". Some library, either NI-VISA itself or a library upon which it depends, could not be loaded. Make sure that NI-VISA and any libraries that it obviously uses (like NI-488 and/or NI-VXI) are installed.
You can also use NI Spy (assuming that you are on a Windows platform) to determine what call is failing. If NI-VISA itself is not loaded, you wouldn't see any entries, of course. But if it is loaded and can't load NI-488, for example, then you would see entries in the NI Spy history window that show what call returned the error.
Dan Mondrik
National Instruments
