I checked back on my Mini running 10.8.3 and Finder won't even open! I forced quit and relaunched it and it just refuses to come up period. I'll try a reboot next, but it appears something is screwed up. 10.8.2 was perfectly stable here so this is a bit of a disappointment something so basic is acting up for no apparent reason (it's been running 24/7 for a couple of days since the upgrade so it took awhile to act up).
It claims I have two windows open in the menu bar, but they will not come to front and restarting it doesn't change anything.
Edit:
I see what the problem is. It was opening the Finder window on my 2nd monitor (which was turned off). In Snow Leopard, I could easily see something like that happening because Spaces would show both monitors content and it would be obvious. Mission Control doesn't show the other monitor and so if it's turned off, you will have no idea if OSX opens something up on that monitor (bad OSX behavior, IMO).