If your not aware of it, the most common on board sound chip is by Realtek.

On April 8, 2011, they released new drivers that fixes the stuttering cut scenes and 5.1 sound drop problems.

If you are having one of these issues and have Realtek on board sound, give the new drivers a shot, they solved both problems for me.

Here's the link to their download page. http://www.realtek.com.tw/downloads/