I created my own function to validate username and password from the login form, and it's working great in FF and Chrome, but does not work in IE 8 and 9.
I'm using hook_form_alter to catch the loginform and then I replace the default validation function "user_login_authenticate_validate" with "my_own_validation_function" in the $form['#validation'] array.
But for some reason the new validation function never gets called in IE, but I've verified that the default validation function is replaced by printing the $form info, and it all looks great.
I'm not really sure of where to go from here, I've spent way to much on this now ;)
Any help appreciated!