After the error I had while Xcode 4.5.2 was trying to connect to the iPhone simulator, take a look to this post. Yesterday I had another proble, I was trying to install the Library docset for iOS 6/5.
The message I received from the Xcode was the following:
Installation path, /Users/gg1/Library/Developer/Shared/
has the wrong ownership or is not writable.
To solve this problem I opened the terminal and then I issued the following commands:
# cd /Users/gg1/Library/Developer/Shared/Documentation/
# sudo chmod 777 DocSets
I don't know if this is uthe correct way to solve this problem, anyway it worked fine for me.