unfortunately, the old themes were not compatible with the upgrade. They have all been removed and I am in the process of searching for some suitable replacements. The one that is the current default is the one I found that was decent, black, white and grey -- and more importantly, I found it quickly.
There are a few options in the theme list now, so you should be able to pick one.... I'll also be looking for one or two others that would suit.
Also... the giant post box should be fixed now.... use CTL-F5 to refresh your browser if it's not...