I cannot reproduce this on the Mac, with or without the new (and much 
slower) Sun renderer.  So I'm guessing it's Sun's windowing code. 
MASON's optimizations push Java pretty hard so I wouldn't be surprised.

More data would be helpful.  What version of MASON are you running?  Is 
it a snapshot or taken off of CVS?

Only while running is telling: this means it's probably something to do 
with MASON blocking waiting for a repaint.

Just for grins, go to sim/display/Display.java, and comment out the 
following line:

                 Utilities.doEnsuredRepaint(header);

Recompile and tell me if it's still doing it.

Sean

Pelle Evensen wrote:
> The hanging only happens when the simulation is running.
> 
> I can quickly produce the hang from the previous post by grabbing the lower
> left corner to resize and then move around violently for at most a few seconds.
> 
> Regards,
>   Pelle