I have tried that extension and it does not work, hence I came up with a simple solution that will work for sure.
For those using the Magento ver. 184.108.40.206 and noticed that Magento is not compatible with IE9 hereunder please find the fix that has proved to work until Magento becomes compliant with IE9
Open up your .htaccess file and add the following two lines at the last
## X-UA-Compatible: IE=8
Header set X-UA-Compatible "IE=EmulateIE8"
This will create an HTTP header that will force IE9 to render in IE8.
I have tried various options but this seems the only one to work 100%.
With best regards