Apple implemented a cool new feature in Snow Leopard: from time to time (I encountered this problem about 5 or 6 times sind 10.6 was initially released) Finder.app will quit and if you try to restart it, OS X will present you with a nifty little error message, namely: „The application Finder can’t be opened (-10810)“.
And, true, once you’re at this stage, Finder can’t be opened again unless you reboot the whole machine. Except if you know you’re way around the Terminal.
Fire up Terminal and enter this command (without the quotation marks) „/System/Library/CoreServices/Finder.app/Contents/MacOS/Finder &“ This will give you a new Finder window and Finder will work without any problems. However, Finder will quit as soon as you close the terminal and you’ll be running into that mystical „-10810“ error again.
To prevent this, add a „disown“ to the command above: „System/Library/CoreServices/Finder.app/Contents/MacOS/Finder & disown“.
However, I recommend rebooting you’re machine as soon as you have a few minutes to spare. I took a look at the Apple forums and it still seems unclear what the underlying problem for this is.