My desktop image keeps changing on its own
Hi all, everytime I log on my desktop image reverts to a previous one I've used. It won't stay on the one I've selected. I've checked it's not set to change every 30 minutes. Is there something I'm missing here, as this just appears to be a glitch?
MacBook Pro (Retina, Mid 2012), OS X Mountain Lion (10.8.2)