if you faced the problem when you're trying to login from front-page login block, with IE10, and you have failed, and you're eventually are using Me Gusta, I Love It, Serpent, try to solve the problem by just replacing the /js/jquery.simplemodal.js file, with the one attached. It's a bug in the library that we had the pleasure to fix.
Also, for fixing the cookie error, on first login, please try to replace the /lib/php/simple_modal_login.class.php file with the attached one. We'll make an update on this, of course, but in the meanwhile you can do the above.
Wish you a great day to you all!