Glad you got this working, but in general there can be a problem with some sound sources not having the "right" kind of header for CDP. Archer Endrich puts it like this:
"One problem that you may encounter is CDP not recognising an input soundfile when it has been made by some other software. This can be caused by non-standard anomalies in the wav header of the soundfile made by the other software. The problem can be rectified by making a CDP copy of this sound with CDP's COPYSFX. This can be run from the Command Line (copysfx infile.wav outfile.wav and see Usage for the various options), or via Soundshaper : Menu – Edit/Mix > SF UTILS > COPY. (COPYSFX is not available in a Soundloom menu.) "
As Simon suggested, run sfprops on the source file and see what it says about the header. Normally CDP will retain the type (output=input), so I'm guessing the problem would have been with the source sound.
Robert