Yikes, since the server move, I'm now getting the stretched post-entry-box issue, too. Firefox 19.0.2 on Xubuntu 12.04, as before (they haven't pushed Firefox 20.0.0 to the repo yet, though I'd expect it to show up within the next day or two).
I notice that the box will scroll along if I type far enough, but this also pushes the Post and Preview buttons aside, too, so I don't dare to see where it actually ends!
