Apple has released a Pro Application Support 4.0 update
that "improves general user interface reliability for Apple's professional applications." Basically, if you use any of the Final Cut Suite apps, Aperture, Final Cut Express HD or Logic products, you'll probably see this in Software Update. Strangely, as with previous
Pro Application Support updates, there isn't a whole lot of extra information as to what this update fixes, or what bugs and quirks it squashes; it's just 6 MB of UI update goodness, I guess.