I've read through my old PM correspondence with OddbOd and re-discovered the solution. You'll have to grab the source archive libao-0.8.8-1-src.tar.bz2 from one of the Cygwin mirrors. Extract that, then extract the .tar.gz file inside it and apply libao-0.8.8-1.src.patch.
After that, enter the libao-0.8.8 directory and change line 45 in src/ao_wmm.c as follows:
"static int debug_flag = 1;" --> "static int debug_flag = 0;"
configure && make && make install, recompile UADE, problem solved!