I'm curious how this is possible, C5 uses jquery which should be cross-browser compatible. However, when I want to edit a Content block, or create a new one, I just get an empty white lightbox. The other blocks seem to work just fine. Anybody have any ideas on this one?

Using latest Firefox stable (Vita & Ubuntu Jaunty) and IE8 (Vista).
Fresh install of concrete5 on a server with safe_mode on, fopen wrappers disabled.