I've made a fix that may or may not solve it. If it doesn't - well, someone go looking for a 2.0 compatible theme that looks nice and fits BM. :-)
Seems to have worked for me in Chrome. The edit box is no longer crazy-wide, and can be resized with the handle in the bottom corner. Well, it can be made taller or shorter, but not narrower or wider. Anyway, works good enough.
