Ok, so there is no fix which make it possible to play the game in IE9?
Why don't you explain this for your client and suggest him to use another browser? As ryanrybot Microsoft isn't fast and focused to improve Internet Explorer as they like to say in every new version.
But if (s)he is a Microsoft-fan to refuse alternatives, you should convince the client to either to upgrade to latest IE version and/or turn the Default Compatibility View off.