Dear Michael McCracken, when navigating through the window for a particular database entry, the key CMD-W for closing the window sometimes does not work. The window remains open with the last edited line shown, see screenshot. It cannot be closed with the mouse on the red button and disappears. Opening the edit window for same database entry again, does not work neither. This bug appeared two or three updates earlier. --C. Henkel.
I cannot reproduce this. Can you say more about when this happens? Did you edit the enttry before closing? (I don't see an edited mark in the close button in your screenshot).
Also, when this happens, is there any log message in the Console?
Are there no logs in Console.app when this happens? You may want to search for "bibdesk" or "edu.ucsd.cs.mmccrack.bibdesk".
Is this fixed in the last release?