Well, it's actually not an upgrade but a downgrade. The last update to 2.20b fixed some errors in making a stand alone EXE, but the #wav bug came with it. If you want the version just before it (it's still version 2.20b), I can upload it somewhere for you. Do you have the standard edition or the powerhouse?
Also, I heard you can get still play WAVs through #mediaplay or #midiplay, but I haven't tried it out.