If you're using the SoundMAX Integrated Digital Audio suond card, sometimes the speakers on the computer suddenly lose sound. The sound also died out and the videos paused at the same time. The only way to fix this was to restart the computer. Then the sound would work again.
You can try the following methods:
1) Make sure that ALL your drivers are up to date.
Uninstall your video card drivers and re-install. Do the same for your sound drivers.
2) Turn off any power savings you use.
Run down the battery then charge it up.
3) Run your antivirus then Spybot.
4) If still the same problems after all the above run a MEM test for yuour RAM.
Driver download for SoundMAX Integrated Digital Audio