Stuck screensaver on OSX.

I lock the screen and step away. When I return the screensaver will not stop. This has happened a couple of times on the Mac Mini running Lion. Sometimes it is just slow to respond but this time I waited about ten minutes.

I did an SSH from another computer and killed the screensaver process. This worked but is very annoying. You must have the SSH enabled ahead of time.

ps ax | grep -i screensaver 

83230   ??  U      3:09.28 /System/Library/Frameworks/ScreenSaver.framework/Versions/A/Resources/ScreenSaverEngine.app/Contents/MacOS/ScreenSaverEngine 

sudo kill  83230