Jerky playback on video (Vimeo)

I noticed that most of the video I watch in Vimeo have that jerky motion (like the streaming jump forward for a split second and goes back to the original streaming). Initially, I blamed it on the video. But then it dawned on me that it could be my computer (7 year old 4 gb ram, dual core) could be the culprit. Test the same video on my newer machine (i7 with 12 gb ram) and the video was normal.

Any suggestion on how to fix it. Adding more ram? Would that do?

Or it is a deeper problem like...

Jerky playback on video (Vimeo)