Xcode 4.6.1 install hangs at "Installing - less than one minute" on Lion

I have been trying to update to Xcode 4.6.1 (from 4.6) on OS X 10.7.5. The install gets most of the way through, then hangs out at "Installing - less than one minute" indefinitely. Based on old threads about similar problems I've ensured iTunes and iTunesHelper are both not running. I've restarted and tried again. What else can I try or look into?

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and I wonder if this has anything to do with it?

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The problem in this case appears to be that the developer site was down. Once it came up, install proceeded without problem.