What steps will reproduce the problem?
1. On a Mac (OS 10.4.11) using Safari (3.2.1)
2. Open phylowidget full
3. Open a new tab, go back to phylowidget tap

What is the expected output? What do you see instead?
The program stops running -- no response to mouseover, clicking, etc.

What version of the product are you using? On what operating system?
See above. I'm using phylowidget from http://www.phylowidget.org/full/index.htm.

Please provide any additional information below.
I've seen the same thing with other processing sketches I've created, but not with demos on the 
processing.org site.