Got a weird one, on this site http://www.limbsandthings.com, Internet Explorer customers (all versions, even 10&11) are unable to search, add to their cart, and login to the control panel. Basically perform any form action without hitting the "This form has expired" CSRF error.
Chrome, Firefox, & Safari users aren't experiencing any issues.
I've tried setting the 'disable_csrf_protection' config setting (not ideal)
$config['disable_csrf_protection'] = "y";
However when that setting is enabled IE users aren't able to login at all (no error message occurs). They are able to perform other form actions.
Another 2.9.2 site I manage for a client, http://www.jerseywatch.com is not experiencing any issues with IE.
Update: Viewing the cookies in Chrome vs. IE showed something interesting. The "exp_csrf_token" cookie is showing up when I inspect it in Chrome, however IE is reporting that the "exp_csrf_token" cookie doesn't exist.