Crash and Freeze
So, I finally found some time to watch bluray moies again. Since I had reinstalled my PC since the last time I watched, I had to do a reinstall PowerDVD 12, which I had bought online.
PowerDVD 12 (even with the newest available patch) kept crashing or freezing when I tried to play the disc, or even when accessing the "TrueTheater"- and Audio- options.
Since
COD4 has a curious bug that prevents it from working when no microphone is plugged in, I remembered that I had disabled my onboard sound card after I bought my USB headphones (Logitech G35).
So yeah,
enabling the sound card fixes the problem. For now.