NIS 2009 Smart Firewall Program Control does not see all exe files

I have NIS 2009 installed on Vista Ultimate 64bit. I am attempting to add WFS.exe (Fax & Scan) to Program Control in order to allow access to a network scanner. However, the list of files displayed by the explorer window launched via the "Add" button is a subset of the actual set of files in the folder (in this case C:/Windows/System32). Please note that the file WFS.exe in my case is not visible in the NIS explorer window whether I choose the 'Executable FIles' filter or the 'All files' filter.

 

I would appreciate any thoughts/hints. I checked some obvious things like Property/Security settings of .exe files that do and do not appear, but cannot spot any differences.