This has been happening for quite a while (since before I upgraded to 10.8, I think), although I'm running 10.8.4 currently; I'm on an iMac from 2012. Every once in a while Finder will freeze up for no readily-identifiable reason. You can click in open windows, but if you change the folder you're looking at it won't display the files. Open File dialogs in programs don't work, either, they just display the Favorites along the left side, and maybe a directory path, but you can't select anything. More often than not, either immediately or eventually you'll get the spinning beach ball of death. I haven't found anything in the Console, but maybe I don't know what to look for.
If you Force Quit, either through the Apple menu, by click-holding on the Dock, or by entering
killall Finder in Terminal, the process does not restart. Files disappear from the desktop and don't come back, and the little highlight below the Doc icon (indicating a program is running) is not there. If you click on the Finder icon the highlight appears, but the Finder windows don't, nor do the desktop items. Running
open /System/Library/CoreServices/Finder.app doesn't work, either. The only way I've found to get it running normally again is to reboot, but there are problems there, too. I'm not sure if it's related to the Finder issue, but if the computer has been running for more than, say, an hour or two, selecting Restart from the Apple menu doesn't actually reboot the computer, it just hangs for a while on the grey screen, without getting to the shutdown log, so I need to do a hard reboot by holding in the power key for a second or two. Sometimes the Finder crash will be so bad that I can't even get to the Restart option, and have to hard reboot right from the GUI.
Any help or suggestions you could give would be very much appreciated!