Why do Apple TV's lock up?
I had a second generation, and now a third generation, and they both locked up---maybe it's Comcast---I don't know, but the last one that locked was because of a software update
Does the actual device "lock up", i.e. needs a hard reboot by pulling the power cord, or does the video just freeze a lot? If the latter, it's your crappy ISP. And believe me, they're ALL crap.
It completely locks up --requires me to connect to iTunes and restore using a micro USB cable---
if you have to keep restoring that way you should take it to genius bar