Xbox 360 Bing hijacking Dashboard

Whenever I boot up my console, end a game, or simply tap guide button and Y, the Bing page shows up instead of my Dashboard. My LB works fine and the hijacking is annoying.
I've tried: 1. delete and re-download my profile; 2. clear cache; 3. update rollback; 4. install offline update.
As long as I sign in Xbox Live, Bing hijacks my Dashboard. If I skip sign-in or sign in with no internet, no Bing, no pain.
Only found one post about 2 months ago: http://www.gamefaqs.com/boards/927749-xbox-360/72011688
Anyone knows how to fix this? I've wasted way more time than expected. Chat with xbox support did provide some plan like rollback and offline update, but didn't work.
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New Xbox 360 Dashboard Walkthrough [12.6.11] - Kinect, Beacon and Bing Support
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