This changed just recently, possibly related to Tom Ball's work fixing
4029595 or 4028014. It seems that buttons will only accept a click at
a specific maximum rate that seems about the time of a double click
timeout.

To reproduce, bring up the ImageFlushTest in the test directory and pound
on the reload button. It should respond as fast as you click, but if you
click quickly it will only respond to every other click or so. If you
click slowly, it will see every click.

If you bring up the ComponentTest you can see that many components ignore
what appear to be double clicks, the buttons and the scrollbar arrows
for example.

These applets work fine on Solaris.