I am strongly using Adobe Premiere Pro for years now, and since I work with the AVCHD Codec I got this problem:
Every time I import a mts file into premiere pro, it got no sound with it. I first tried this with premiere pro cs4 (last update). There it worked properly. Then I upgraded to cs5, and suddenly the problem was there. I reinstalled the application, I installed all sorts of codecs, etc etc... nothing worked. Then I upgraded to premiere pro cs5.5, and the sound was back. Just as normal as it should be! And now, that I have premiere pro cs6, the sound is gone again...
It's just really annoying and sometimes even preventing me from doing my work! Because when I have really really much footage to import, I have to convert it to mp4 first!
Please, I don't know what to do any more, this is driving me crazy!
My best recommendation is to wipe your system and reinstall everything from scratch, from Windows on up.
And only install what you need for a production rig, use another computer for anything not directly production related.