Plugin crash when closing IE10 running Boccia game.

Repro Steps:

1. Install 4.0f7 and set channel to release
2. Launch IE10 with http://paralympics.channel4.com/boccia/
3. Start to play a game
4. Close browser
5. Observe crash of plugin

Desried outcome: No crash when closing browser running content.

Log file attached.

Reproduces with FF 17.0, Win 7 and 4.0.1f1 plugin and runtime files.