How do I fix an app that's stuck in application switcher? I'm running OS X 10.7.5 "Lion". Three times now, Preview.app has gotten in a state where its icon is visible in the application switcher (⌘+Tab) but it isn't running (doesn't show up in ps ax in the Terminal) and will not start (e.g. double-clicking a PDF document).

I've tried killall Dock, killall SystemUIServer, and killall Finder and those do restart but the stuck Preview icon is still in the application switcher. I've also tried removing the saved state under Library > Containers > com.apple.Preview but that doesn't work either. The only thing that solves it is logging out and back in again.

Is there some way to get this unstuck without having to log out?
In Terminal.app, find the process ID for Dock with the ps aux | grep Dock command and kill it with the kill -9 PID command. An example:

$ ps aux | grep Dock
username              290   0.0  0.4  2730344  34500   ??  S    Fri08PM   0:22.48 /System/Library/CoreServices/Dock.app/Contents/MacOS/Dock
username             3633   0.0  0.0  2432784    612 s000  S+    8:06PM   0:00.00 grep Dock
$ kill -9 290