This is due to the multi column changes. Technically speaking, I don't think it's incorrect (though I think it may expand out to the whole window width which would be wrong). I believe we only actually specify a min-width for the menu, so it's somewhat free to expand.
(I should note that this doesn't happen in Chrome.)
Partially fixed. I've handled this case, but I think it's a bit of a browser issue in terms of how it lays out inline-block elements. The inline-block handling is necessary to prevent breaks within the columns in other cases.