I know this post is 3 years old, but on Google, it's one of the first posts to come up and there is no solution. However, after experiencing the same problem, I did a little of my own trouble shooting. Are you using a wireless connection? I was, and that's what caused the occasional freezing. Every so often, data would stop being sent for a couple of seconds, before resuming. So beware, if you're going to play TF2 with wireless internet, make sure you've got a very good signal, or try and use wired internet if you can.
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