Mac OS X Desktop Background is gray

One thing which bugged me was that every now and then my desktop background on my Mac Book Pro would turn plain medium gray at tome point. I cannot even tell when this happens. Trying to reset the background image will not help when this occurs.

(I am using an external monitor connected to the Mac Book Pro and I put this configuration to sleep and I turn the monitor off at least once a day. I do not power down or reboot the laptop at all unless absolutely necessary.)

Logging out and back in solves the problem, but is of course tedious. I found a better workaround here: http://reviews.cnet.com/8301-13727_7-57389668-263/os-x-desktop-backgrounds-gray-after-waking-from-sleep/

• open a Terminal 
• type: killall Dock

The background image is managed by the Dock application which automatically restarts when killed. This is of course not a solution, but is a rather easy way to 'fix' this, until it happens again. :-)