I was trying the BlockUI plugin - we're about to implement it with one of our products at work. The current way that we do things doesn't display right in Linux (Firefox). (Actually, it doesn't display very well at all, which is why we're moving to BlockUI anyway.)
It turns out that BlockUI still does a better job, but the overlay (the grayed-out background) doesn't appear at all. The dialogs still work fine, but it's harder to notice without a grayed background. I'm testing this in Fedora 10, using the default Firefox installation (up- to-date). Is there a way to get this to work?
