From what I understand this blocks ISP YouTube cache servers...which seem overloaded for some, and this defaults you back to Google's data center.
If you have 3rd party router software such as DD-WRT or Tomato, telnet into your router and run these two commands:
iptables -I INPUT -s 206.111.0.0/16 -j DROP
iptables -I INPUT -s 173.194.55.0/24 -j DROP
If not, you can use this guide to block the ip's on each windows machine:
GuideThe first range worked for me on TWC, the second range worked for me on U-Verse, I decide to just block both. This fixed all my youtube problems, no more choppy playback or buffering problems even at 1080p.