I don't quite understand but some videos I have no problems with but most 720p videos encoded in h.264 seems to chug every few secs to every few mins. The video freezes and audio keeps on going.

Any reason why this would be the case?

I use VLC to play them.

I have a first generation Macbook upgraded to 2GB of RAM.

At first I figured maybe I'm limited by my hardware (the integrated video card likely?) but I noticed that people with weaker specs could run them without a problem.

Thanks in advance for helpful responses.