You might find something in the archives about that issue. As far as I remember it has to do with the compatibility mode of IE which is used when its hosted as an embedded browser control.
You can only change that behaviour by modifying the registry or by modifying the compatibility header in the HTML which hosts your script.
Here f.i. this issue is discussed: https://stackoverflow.com/questions/17922308/use-latest-version-of-internet-explorer-in-the-webbrowser-control