I've seen a few mentions of what might be this problem elsewhere, but haven't found any real information.I'm using community/e-svn with extra/nvidia and compositing enabled. I'm getting unwanted black boxes appear where various effects are happening.
boxes.thomasjensen.com boxes is a text filter which can draw ASCII art boxes around its input text. These boxes may also be removed, even if they have been badly damaged by editing of the text inside. Since boxes may be open on any side, boxes can also be used to create regional comments in any programming [...]