Single desktop image for all desktops I upgraded from Snow Leopard to Lion. Afterward when I would set a Desktop picture (either through System Preferences or iPhoto) it was applied to all desktops.

Yesterday I control clicked the desktop and set a picture and it was only applied to that desktop. Now, wether I use System Preferences or iPhoto it only affects the current desktop. I then have to move SP or iP to a new desktop and set that one, then the next, etc.

Does anybody know how to fool Lion back to having single desktop picture for all desktops?

Edit:
I have active windows on each desktop that I would like to stay there, so closing all of my apps and regenerating desktops is not helpful. Similarly, gathering all windows to a single desktop and regenerating desktops is again not helpful.

The point is to reduce tedium, so anything that involves more steps is clearly not what I'm after.

To be explicit, for some reason previously Lion did it the way I want. Some setting in some file somewhere changed this behavior. This is the setting I'm looking for.
The answer is simple (and very Apple-like!).

Simply close all extra desktops until you only have one desktop. (To do this, go to Mission Control, hold down alt and click the crosses which appear on unwanted desktops).

Then change the desktop background for the one remaining desktop.

Now any new desktops you create will inherit the background of that first desktop.