NikonScan4.ds could not be loaded

I have used the suggested workaround from the Windows 7 forums (Getting your Nikon Coolscan to work on W7 x64 - Windows 7 Help Forums) to get Nikon Scan 4 to run under Windows 8 64-bit. It worked fine for a while. Now when I try to run it, I get the message C:\Windows\Twain_32\Nikon\Nikon Scan 4.0\NikonScan4.ds could not be loaded. I checked the directory and NikonScan4.ds is in the indicated directory.

Any ideas why this might have begun occurring or how to go about fixing it?

StlSailor