When logging in lubuntu 12.04, my background image always disappears, leaving the screen with color only and then I have to go to definitions and set the image in the background again.

I notice that this does not happen with low-resolution images, only with high ones, but also happens with images that fit my screen resolution (1280 X 720).

Any ideas on how to fix this?

The image remains at it's location, but on the desktop preferences, the pathway to the file location is lost and set to none.