If cursor is focused in inputbox of find or replace strip dialog, and user presses Ctrl+Z, then Undo is executed in editor text pane instead on action in focused inputbox. I don't know of application that does the same (i.e. undo is executed on inputbox actions if supported or not at all if not supported, AFAIK), and have no idea if it's known issue, bug, or feature, but thought to comment on it as it's unexpected behavior IMHO
This is currently on XP SP3, but perhaps it's same elsewhere