Version: 2.3.5 (using 3.5.9, Kubuntu (hardy) 4:3.5.9-0ubuntu7.1) Compiler: Target: i486-linux-gnu OS: Linux (i686) release 2.6.24-16-generic FLAC files do not play. When a FLAC file comes up on the playlist, all buttons except Play become disabled, the Play button does nothing, and the playlist does not advance. (The metadata displays just fine.) In juk-kde4 I did not have this problem, but I cannot go back to juk-kde4 until bug 233842 is fixed. The FLAC codec is definitely installed, since I can rip CDs to FLAC using KAudioCreator. Tried installing libarts1-xine; still doesn't work.
There are two requirements for file playback. Playback has to be supported by the backend (either aRts, gstreamer, or aKode), and the file type has to be supported by taglib. The fact that the file showed up in the list means it is supported by taglib. If it doesn't play you can try selecting a different backend from the Player menu (Player -> Output To). Make sure whichever backend you use supports FLAC playback (and it's not as simple as being able to encode FLAC unfortunately).