The Pandas are coming... and with the 5.0.4 patch today, Cynwise has decided that the best thing you can do is to start over from scratch.
Well, not entirely - not until you have the chance to level yourself some Panda. But for your existing characters? There have been enough changes that is makes sense to clear off those menu bars and rebuild 'em.
From my time in the beta, I'd have to say this is a pretty sound bit of advice. Things have changed drastically; instead of adapting, it's probably best to start over and build a new UI that you're comfortable with.