I performed an upgrade from 6.0.1 to 6.0.2 and experienced no problems; the upgrade went just as perfectly as every other time I've performed it.
However, this time, the web UI seems to be broken. The usual login form is displayed, and after login, the "Loading..." splash is displayed, and this is where it stays. This ocurrs on IE7, IE8, FF3, and Safari 4 -- so I'm certain it's the web UI. In IE, the words "undefined" appear all over this splash page. I think I was able to get the Standard HTML UI to load, though, so perhaps the Ajax is what's broke.
Re-installing does nothing. And, of course, I can't downgrade. No one else is reporting this issue, so apparently, the moons have aligned just for me. I'd like some pointers on where to look.