Apple Lossless doesn't go through MC's internal playback engine (it uses QuickTime and Directshow). You should try some other format instead. Also iTunes does not use ASIO. For testing your ASIO driver you should try some other ASIO aware player program.
Personally, I have no problems with ASIO playback. I have a Terratec DMX 6fire 24/96 soundcard and I can use the Terratec or the ASIO4ALL driver (though I have not recently updated the ASIO4ALL driver). It doesn't matter what audio file format I play as long as it is one of the internally decoded formats. Wave, MP3, APE, FLAC, Ogg, etc work.
Several months ago an early beta build of MC had some wav related problems, but I assume your are using the latest MC12 build.
Have you checked that the ASIO settings are similar with your old MC11 ASIO settings? Have you installed anything else besides MC12 since ASIO playback worked the last time? Do the Direct Sound and Wave output modes work normally?
Please post additional info. Your soundcard model and driver version, your system info (from MC's Help menu), etc.