Committed workaround in demo page to the 3.3 EE maintenance branch at revision 44656 and to the P03 tag at revision 44655.
I could also reproduce this issue on IE9 and IE10.
This is an issue with the browser itself, where the media player plugin remains visible after removing it's container node on the page.
After trying different tricks and workarounds what actually worked was simply moving the container node -1000 pixels to the left, so it's out of sight, when navigating to a different demo.
I couldn't get ice.onElementUpdate() to work on any of the involved nodes (form, container panel group, and the object tag itself), so the workaround is more elaborate and it involves adding an event listener to all menu links on the left and invoking a function to hide the media player plugin and then removing this event listener from all the menu links.
Need to see if there's anything we can do to correct this apparent browser defect.