I am running ubuntu on my netbook and use vlc media player, for some reason when I play 720p videos they get choppy and freeze constantly, is there a way around this or the videocard that comes with the netbook is having problems supporting it ?
VLC is a great player so that's not the issue. However, you might be able to play around with the video settings.
This most likely a codec issue or a hardware issue. Make sure you have the restricted formats package install in Ubuntu (https://help.ubuntu.com/community/RestrictedFormats). If possible, could you post which codecs are used to encode your videos? You could be using old or wrong codecs to decode your video. Resulting in only partial success. My buddy had 720p video playing very well on his netbook after some codec tweaks.
Seeing as this is a netbook, it might not have all the power needed to render the video perfectly. This would result in dropped frames and "choppy" video. Try playing the video using VLC on another computer, preferably a desktop computer. Does the same thing happen?
vlc does not use gpu acceleration as a default, and even when activated it's experimental as of now. Check http://wiki.videolan.org/VLC_GPU_Decoding for prerequisites and codecs.
Assuming it's not activated your cpu (netbook = atom?) most likely has difficulties to keep pace.
Have you tried mplayer?