Changing desktop background in OS X 10.8 only changes it for the current desktop space I'm experiencing  a bug in Mountain Lion. I have 2 desktop spaces open. When I change the desktop background picture, it only changes for one of the spaces and not the other. Rebooting solved the problem.

Is this a bug? If so what is causing it? Is there any way to change the behaviour?
Seems like if you set the first desktop to the picture you want and then go to each space and right click on the desktop and select "Change Desktop Background" it changes that desktop's background to the background of Desktop 1.

YMMV: This in  10.8.1, pretty sure it wasn't like that before (in 10.8).