David,

Let's see if we can get closer. Here's another thing to try:

BalloonEngine resetStats.
BalloonEngine doProfileStats: true.
	Display deferUpdates: true.
	1 to: 100 do:[:i| 
		(BalloonCanvas on: Display) 
			drawRectangle: Display boundingBox 
			color: Color red 
			borderWidth: 0 
			borderColor: nil].
	Display deferUpdates: false.
BalloonEngine printStats.

This will print information (to the Transcript) about the internal time
spent in interesting areas of the engine. Could you try this on both
versions?!

Thanks,

  - Andreas