Try opening the file in CD Wave Editor (a very forgiving program). My SD633 does stereo as a two-track poly wave, and Wavelab 6 can't see anything there, looks like it recorded nothing. CD Wave sees a header that says a zero bit file but lets you opt to ignore it, opens it fine, then saves in a format Wavelab can handle. I don't know if your problem is something similar, but it is worth a shot.
Jeff