It might be helpful if you itemised your system components in order give the people here a better insight into how your PC setup is arranged. At the moment there is nothing to go on.
Sounds like you are having some of the same issues as others....myself included.
1. The audio stops playing .. typically, when this happens to me it is a single audio clip. Other audio clips, before and after the one that does not play .. they play fine. I posted a question about this recently and found others also had this problem. Sadly, there apparently isn't a "fix" .. however, when this happens to me, I find if I make some type of change to the audio clip (increase or decrease the db level, if even just .1db for example) after the 'new audio render' the clip will again play.
2. When the video freezes, is that in the Monitor window and if so, do you have your Playback Settings set to play the video to an external monitor? If you do, that's 'another issue' with CS4 ... The video in the external monitor continues to play, but the Adobe Monitor Window freezes ... no known fix of which I'm aware.
no known fix of which I'm aware
Actually, there might be. Per Harm's suggestion, details on:
4.) Operations being performed
might help someone spot a common aspect and a solution will likely be forthcoming. If not a solution, someone will definitely have a workaround, until Adobe can address the issue with an update.
In the meantime, you might want to file a Bug Report, but do be ready to furnish all of the details, so that Adobe can replicate the problem.