Installing Xcode 4.1 Issue

I am installing Xcode 4.1. I downloaded it from the App Store (on Lion) and now it's been more than an hour "Updating Files". When I click Xcode however, Xcode opens up in 4.1. What is this? Is this normal? Can I just force 开发者_StackOverflow中文版quit Xcode? Did it upgrade but just hang?

Thank you

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Since at the end of the process I was still able to fire up Xcode 4.1, I just quit the installer and restarted it. It took 30 minutes or so and it was completed. Everything works now.