It is hard giving any suggestions without a file to view. What file
type is it? Can we view one so we can see the problem for ourselves? IE
is just a browser and a poor one at that. What add on is used to view
the file? I use an Acer netbook but have had no problems setting it up
with 12.04 and watching any video in firefox.

If alternate videos are available converters before watching may be an
answer. The download speed may hender smooth rendering. It may be that
the video is raw video, if that is the case then maybe a complete
download before watching would do the trick. More info please.