I've figured out that the problem is only with the Build Settings tab. So I am rewriting this post...
If I select the project in the project navigator then click on Build Settings xCode hangs with the pin wheel several minutes. After I finally getting into Build Settings and as long as I have the project selected, any movement of the mouse or click will make it hang again. I have to get out of Build Settings to get things back to normal.
I have tried cleaning the project and ultimately uninstalling/reinstalling xCode.
I don't know if this is related, but since upgrading to this version of xCode I have had numerous long wait times trying to build or build and run this app. It indicates that it is paused indexing. This does not happen all the time, only on occasion and usually when first starting up xCode.
Any suggestions?
Thanks,
John
Check you Keychain.
I had exactly the same problem. I even erased Xcode from my system and reinstalled, but nothing seemed to help. No problem on other useraccounts though.
I finally checked my Keychain and found a tremendous amount of keys for my MobileMe account. My best guess is that iPhoto, Aperture or another app failed to connect to a MobileMe server, and stored a key on every attempt. Endresult was a login.keychain file of 12.1 MB. I can imagine Xcode choked on this big keychain.
Deleted all these duplicate keys and my login.keychain is around 600KB (and even fits on one floppy ;-)
All my problems with Xcode 4.3.3 slowing down on Build Settings are gone.
Uninstall, reinstall. That's the solution that I've seen works best with Xcode's occasional flare-ups.
来源：https://stackoverflow.com/questions/10404560/xcode-long-freezes-after-upgrading-to-4-3-2