Support Installing OTA Jelly Bean update on Galaxy Nexus after previously rooting

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http://androidforums.com – Just today I took over my friend's Galaxy Nexus. He had previously rooted it and installed Jelly Bean on it, but hasn't touched it for about 6 weeks. So I got it today and immediately noticed the official OTA Jelly Bean update was available. I (perhaps naively) decided to DL and install the update. Right now it's stuck on the operating-on-Android screen with a warning sign and has been for about 2 hours. What should I do? I'm wondering if it's stuck in some broken state because I tried to install the official update after a previous root. (General)