I've noticed that when running under the latest version of Java on OS  
X, simulations will run fine under 2D visualization, then suddenly  
drop to half their speed for a few seconds, then jump up to full speed  
again, and back down, and so on.  I'm trying to nail down what might  
be the problem.  I regressed to very early versions of MASON and  
they're all having the problem so I suspect it may be something  
tickled by Apple.  However I can't reproduce it with simple animation  
tests outside of MASON.  Has anyone else seen this?

Sean