Little problem with ghost styles…

I think it has something to do with the new contact form. Left it as it on my blog mathiasblog.com on the about page. See how the Newsletter register input is way too large?, it doesn’t show that way on other page, nor posts.
Why? That’s what I’m asking.

I checked it out with firebug, there’s a style that gives it 100% width. Tried to override that style with another !important note but nothing helps.

Please, this is urgent…