I was finally able to get rid of the "WebM Beta" links and get the 480p mode back by opting out of the HTML5 trial, which I didn't even know I was opted into until I read through this topic.

IE 9.0.8

When I was on one of the pages with the "Try the WebM Beta" or whatever link, the 480p mode would be missing leaving 360p as the ONLY resolution option for many videos. Also, buffering would be much slower and the playback/buffering progress bar would not drop down after I moved the mouse pointer off of it. It would stay raised up, covering the bottom edge of the video frame.