This is a mac-only bug, so I figured I'd bypass the troy->michaelp->pierre by assiging directly to pierre ;) In apprunner, the toolbar area at the top is set with a style that has "position: fixed" in mozilla/xpfe/browser/src/appshell.html. With it set this way, the toolbar doesn't get any events (the url bar is inactive and the grippies don't exhibit their rollover behavior). When this position is set to "relative", everything works fine and events are processed again.

Another bug was reported against fixed positioning: 3100.

Fixed.

Fixed in March 25th Build.