WavPack Cowon O2 Answer
You have to rip the CD without the correction file. This will produce a .wv only that is lossless. The two file method produces a lossy file (.wv) combined with a correction file (.wvc) that together is tech lossless. This does not work on the O2 it will only see the .wv high bitrate lossy file. I have the O2 and use DBPower Amp to rip my CD's and the .wv files play just fine on my O2.
Also I have noticed the .wv files are a smaller size than a level 8 .flac file. It is also worth mentioning that tech .wv uses less power to decode. This should equal better battery life. I am in the process of testing this now.