When attempting to add a contact to the personal address book that already exists, the duplicate address warning window pops up, then starts expanding horizontally until the window is closed by right-clicking on the top border - hitting alt-f4 doesn't work, either. The buttons are no longer accessible because they have expanded off the screen.

1, Add an address to the personal address book by right-clicking the address in a received email and select "Add to Address Book".

2. Right click on the address again and attempt to add it as a duplicate entry.

3. Watch the window grow.

Actual results: Window begins to maximize itself horizontally, then extends off the screen to the right, taking the Cancel, Add, and Merge buttons with it.

Expected results:
Window should stay where it is and allow you to cancel, add, or merge the contact.

Evolution 3.10.1 in Fedora Core 20 Beta.