My uploaded youtube videos are very choppy....

I am very new to this, I'm a big football fan and I have been recording football games on my computer through a Hauppage 1600 in 720p

I edit the videos in WMM, when i publish the movies i do them in 640 x 480 to make it easier on youtube to do it's job, I'd like to do them in high quality if possible, I'm pretty sure it's mpeg-2

but when i uploaded my first movie, the video came in very choppy even though it looks just fine on my computer in it's dowgraded format, the audio is fine