Rockbox

I'm guessing one of them has a backdrop, and one of them doesn't, and it ends up using the backdrop set by the old one. I think that backdrop priority doesn't quite work out yet.

Part of the problem is that WPSes should be able to set background colors internally, much like you can for the menus. Then, if a WPS sets one, it overrides the current backdrop with a solid colour of whatever is set, allowing the clearing of backdrops to white or some other color, and allowing solid-backdrop WPSes to work even when you have a menu backdrop, without having to use a solid bitmap for them.

sure i agree but I don't remember that happening in the past

while trying to fix this:
Additional bug: if you clear the backdrop from within the wps screen, the wps code doesn't notice the clearing and will restore the old backdrop again whenever leaving the wps...