I've had 2 machines this week to suffer this problem. When creating a new message, replying to a message, forwarding, etc. - anything that uses the message composition/editor window - and the user attempts to use the address book via the "To:" or "CC:" or address book buttons, the contact list fails to appear and Outlook hangs. Neither of the windows will take focus, and right-clicking the Windows taskbar buttons has no effect. The app must then be shut down with Task Manager.
The address book will show up just fine when using the button in the main Outlook window. The contacts list appears as expected when viewing from the main Outlook window.
The first problem machine started working after running a repair on the Office installation. That didn't work on the second machine (several attempts). I tested a new profile, but the problem also existed in the new profile. I used the PST repair tool on outlook.pst, but that also failed to solve the problem. I moved the contacts to a different folder, but the problem persisted. And just this morning, I uninstalled and re-installed Outlook, but the problem is still there.
Any ideas what I'm missing here? Or other troubleshooting suggestions?