I got a problem: after I open gscan2pdf an info window appears saying:

   Save as DjVu requires djvulibre-bin
   unpaper missing
   OCR requires gocr, tesseract, ocropus, or cuneiform

after I close that window the little progress bar then runs back and forth as it is "opening device".  Then an info window appears saying, :

   "Error opening device: Invalid argument"

It was working. It was doing this with gscan2pdf version 1.2.3 (the apt version) so I updated  it to version 1.2.6 but it was still doing it. I googled 'gscan2pdf "Error opening device: Invalid argument"' but their were only 4 results. The only one of which might have helped said to: 

   rm  ~/user/.gscan2pdf
   rm: cannot remove ‘/home/bmike1/user/.gscan2pdf’: No such file or  
      directory

I then  ran apt-get for the programs it said were missing and now only the "Error opening device: Invalid argument" info window appears.

Any ideas as to how to resolve this?

:-)~MIKE~(-: