>The following line works fine on my development PC but causes an error when the application is installed on a users PC.
>
>modi comm "c:\program files\freemansoftware\tip\fedcodes.txt"
>
>The error is an invalid path or filename. I can't for the life of me figure out what's wrong.

Wouldn't MODI FILE be more appropriate here? I don't even know if MODI COMM works in runtime only installations. That said, have you verified that the path exists? For example,

IF !FILE("c:\program files\freemansoftware\tip\fedcodes.txt")
  MESSAGEBOX( "Oops! " + "c:\program files\freemansoftware\tip\fedcodes.txt does not exist", 0 )
ELSE
  modi comm "c:\program files\freemansoftware\tip\fedcodes.txt"
ENDIF