After several failed attempts to connect to iDisk in 10.6 (e.g. poor internet connection), Finder tends to crash with the error:
The application "Finder" cannot be opened
-10810
Finder then will not automatically restart. But there is a fix if you have Spotlight, Quicksilver, Google Quicksearch box, or some other access to Terminal. If you do, launch Terminal and type killall Finder, then press Return. Finder, although apparently not an active process (per the above error), will then restart immediately and successfully.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20090831170217804