I dunno what to tell you, it works just fine for me.
I installed MakeMKV, and ripped my copy of Transformers 3 to disc, with only the Video and the TrueHD audio track.
I don't have MB, so i tried in WMC directly, and it plays just fine. I'm not bitstreaming though, i would suggest to turn that off as the first thing when you notice some kind of trouble.
This setup is of course LAV Splitter with LAV Audio (and Microsofts H264 decoder, because i was too lazy to override that)
I got some playback failure when i accidentally had Haali setup as the MKV splitter from some earlier testing, though, but thats to be expected, it doesnt do too well with TrueHD. I'm not sure what big benefits Haali has in the peoples minds producing those codec packs, the only feature not present in LAV is the "Ordered Chapters" in MKVs, but the only people that ever use that are Anime people, which i would claim are not in a majority (of course i could be wrong