WAM, WAC, WAD, and WAA are all from Beyond Good and Evil. Although Ubisoft made BG&E, as well as Raving Rabids, I'm not in the least surprised that they don't work. The PC version of BG&E was also WAM, WAC, WAD, and WAA and they don't work either. I'm just saying that even though Winamp might associate itself with various files, it does so based on file extension, not file format (which is an internal (to the file) thing. It's much easier for programs to associate with an extension than it is to scan a file to find out what it is). Winamp supports WAD and GCM (BG&E and LEGO Star Wars), but both of those are formats that existed previous to in_cube. WAD is used by DOOM (and many other games), and GCM is a Gamecube disc image. In_cube won't be able to play either of those, even though the extensions are the same.
Hopefully you realize all this. The only reason I bring it up though is because it seems that people expect in_cube to work with any file that it "supports" even though the files in question are very much entirely different (different game, different developer etc.).
Anyway, thanks for uploading the file. That is usually the best way to get things sorted out, rather than saying "It says it's supported! Why isn't it working?" As I said above, don't expect a file to work just because it's "supported." Of course, by all means give it a try, but it's far more rare for it to work than for it to fail. Mouser X over and out.