Dear franzk,
This error is usually associated with currupt installations of NI-VXI. Some older versions of NI-VXI also could cause this error. I suggest you uninstall your current installation of NI-VXI and upgrade to the latest version. The latest version of NI-VXI is NI-VXI 3.3 and can be found at http://www.ni.com/support/vxi/drivers.htm For more information on similar errors, please review KnowledgeBase 2X7D85RA: Why does the InitVXILibrary function return -1? at http://digital.ni.com/public.nsf/websearch/3470C41C514FBCE486256D200069DE1A?OpenDocument
Regards,
David Shatila
Applications Engineer
National Instruments
http://www.ni.com/support