Hi I just found this site and was browsing around when I stumbled upon this thread. I thought I could help by conducting the experiment outlined by Eloise:
~> flac -s original.wav -o original.flac
~> flac -d -s original.flac -o copy.wav
~> md5sum *.wav
eec4543432b0bad0e61ceb9aa0ffa83f copy.wav
eec4543432b0bad0e61ceb9aa0ffa83f original.wav
~> ls -s1h *.wav *.flac
48M copy.wav
30M original.flac
48M original.wav
That should lay that one dead. If you can hear any difference between a wav and a flac, you either have a buggy decoder or a vivid imagination