Are you using MB 3.1, or 3.2? When I updated to 3.2, one of the first things I noticed is that the volume slider now reverts to showing a numerical value by default. Clicking the number shows the bar again and allows you to adjust, then will revert back to numerical. I just made +/- hotkeys so I don't even have to click there anymore. In 3.1, the number showed up only when there wasn't enough horizontal "room" for the bar, in my experience, as described by redwing. My player controls are in the bottom pane.