I'm not sure if there is a way to solve this in a nice way, but I've been facing this problem quite often lately, and it's always painful. If I have a Firefox window with 15 tabs open, and some popups, of which I've forgot, and I close the big window first, and then popups, then guess what gets restored upon next launch of Firefox. Right. The last close popup window, but this time it has all default bars et cetera. This really hurts. Maybe Firefox should not account pop-up windows as last closed, and only look at full-featured (i.e. multi-tab) windows in such cases?