Weird, don't know how it happened but my 360 S had been freezing up at the dashboard. But if I played a game, no issues, no freezing, ever. Just at the dashboard or any dashboard related items....avatar editor, Netflix, videos, etc.
So, I thought it was an Xbox problem and spent hours troubleshooting, reinstalling the latest dashboard update, etc.
So, I swapped routers to test. Sure enough no issues after swapping routers (to DIR-857). Knowing that my 865L was rock solid for months, I saved my configuration files and reset the 865L to default. I'm using FW 1.03. I then uploaded my saved config file but the issue came back.
Reset to default again and reconfigured from scratch. Issue gone.
Hope this helps anyone chasing an XBOX dashboard freezing problem.