Hello,
Does the program actually close, or just the window? If Address Book is still running, you'll see the Address Book menubar at the top of the screen and a triangle on the dock under the Address Book icon. And if that's the case, try clicking on the icon again, and hopefully the window will show up.
If the program entirely quits, then you might want to try using Disk Utility (/Applications/Utilities) to run a "repair permissions" on your hard drive. And if that doesn't help, your records may be corrupted. Open a new Finder window, navigate to ~/Library/Application Support, and rename the folder "Address Book" to something like "Address Book.bak". Then try opening Address Book again, and if it works, you can slowly import your contacts back in.
John A
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