Ok, I found a work-around. As you suggested, I turned off compiz in Gnome (System->Preferences->Appearance->Visual Effects->None) and now everything works as normal again. When I turn compiz on again ('Normal effects'), the apps go in 'true' full screen again.
Ok, I found a work-around. As you suggested, I turned off compiz in Gnome (System- >Preferences- >Appearance- >Visual Effects->None) and now everything works as normal again. When I turn compiz on again ('Normal effects'), the apps go in 'true' full screen again.