A. I can't hear anything when playing from youtube and other sites. when I use DVDs, netflix on demand, and iTunes, the audio works fine. what might be the problem?
B. the audio bottons on the keyboard stopped working.
A) Sounds like a flash player problem:- http://www.mydigitallife.info/2007/08/15/adobe-flash-no-sound-wavemapper-trick/
Also try google, there are plenty of solutions available.
B) Reinstall hotkey drivers.
Maliha (I don't work for lenovo)ThinkPads:- T400[Win 7], T60[Win 7], IBM 240[Win XP]