Steps to reproduce: 1. Install GreaseMonkey (enabling it with Nightly Tester Tools, if you need it) 2. Install Jesse's "TidyBox" user-script from https://www.squarefree.com/userscripts/tidybox.user.js 3. Load URL ( http://tinderbox.mozilla.org/showbuilds.cgi?tree=Firefox ). ** Note that TidyBox shrinks it 4. Move mouse cursor back and forth & up and down over the page, making the translucent popup-divs appear with information about each build) EXPECTED RESULTS: Translucent popup-divs should disappear when mouse moves away from them. ACTUAL RESULTS: Various pieces of the popup-divs remain visible after the mouse has moved away. Note: If I alt-tab or press "Print Screen", the pieces disappear, which makes me think this is an invalidation issue. User Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1b1pre) Gecko/20080904020553 Minefield/3.1b1pre

Are you still seeing this in a build from after the re-landing of bug 376662? The initial landing was backed out due to another invalidation bug (bug 453661).

Yup, looks fixed. I just verified that it's still broken using the nightly build from Comment 0, but it's fixed in these nightly builds: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1b1pre) Gecko/20080905020631 Minefield/3.1b1pre Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1b1pre) Gecko/20080906020434 Minefield/3.1b1pre