I've frequently used Special Characters, accessed with Command ⌘+Option ⌥+T, and have been able to insert characters into text fields by double-clicking them. However, this has stopped working. I can still bring up the Special Characters window and navigate through it, but double-clicking an entry only adds it to the Recently Used section - it doesn't actually insert them into the focused text field. The window also seems to act as if it's not in focus, as the various UI elements inside the window are highlighted with grey rather than blue. Clicking inside the window does not focus it, and clicking on the title bar only focuses the title bar, and not the rest of the window, as can be seen below:
Do any of you have an idea as to what might be the cause of this? As far as I'm aware I haven't changed anything between when it worked and when it stopped working.