Desktop's gone white

Very strange problem has just occurred when I started up my Macbook. My wallpaper seems to have gone walk abouts, and has been replaced with a solid white background.

The strange thing is you can see my original wallpaper when OS X is starting up, but soon as everything loads it disappears and the white background appears. Also, the menu bar is displaying still as though my original wallpaper is on.

The only thing that's as changed has been the 10.5.2 and graphical update. Anyone any ideas?

Problem solved. The culprit was InstantShot. The setting "show background window" had somehow been set. Simply turn it off, and hello wallpaper. 🙂