After doing some Googling on this one, I tried all the proposed fixes: delete cookies, clear temp files/cache, etc… nothing helped in my client’s environment. After doing some testing I found that the new version of AVG Internet Security (version 11) causes YouTube channel videos to report “bad response from server” when clicking from channels. Once AVG was uninstalled, the channels work as intended with no errors. If you don’t use AVG, I’d suggest removing your anti-virus/Internet security to see if the problem still manifests itself. If not, you can start the troubleshooting process for your particular environment.
The fix (although not a great one) for AVG was to remove the LinkScanner components: AVG Search-Shield and Surf-Shield. Problem Solved!
Hope this helps someone out there banging their heads against the wall on this one!