I would not care if only IE 7 was broken, sadly, even IE 10 doesn't work ok.
Were you using that floaty login thing before? Is it part of the theme? Have you tried using the normal login? You could use a conditional to show a link to the fall back login for IE users. Clunky though.
Yes it is part of the theme that's why I have not tried normal login.
Did not work... after editing the forum it did not worked good at all. It was all messed up. Think I'll try again...
EDIT: Forget to delete some code, this login looks good but sadly still doen't help IE users.