Thanks for your enquiry. The error you mention is not an ExportWiz error. It is a system level error.
It is most likely is something to do with the way your system is set-up. ExportWiz is a Lotus Notes database so needs to be opened in Lotus Notes. It may be that you system is trying to open the file as a document and does not have an association to the nsf file extension.
You may need to open Lotus Notes and then choose "File" - "Database" - "Open" and select ExportWiz from the list.
Please let me know if this helps.
You can also try to reduce the number of font in your system and then restart your PC.