So you installed the latest Xcode 5 DP hotness and … it crashes hard every launch?
The trick here is, it looks at the same folder your out Xcode 4 install does for plugins:
… and as a rule They Just Won’t Get On with the shiny new ARC-ified Xcode. So what you want to do is delete or rename that folder, and you’ll be good! Well, good as you can be without Alcatraz and all the other goodies you’ve pimped out Xcode 4 with, but progress is never painless, right?