Open (e.g.) http://jmol.sourceforge.net/demo/trace/ in a tab, create a new tab and (again) go to http://jmol.sourceforge.net/demo/trace/ in the new tab. Switching between each tab shows a running Jmol applet in each.
Same instructions as above. Only the applet in the newest tab works, the older tab has an applet that is black background, no molecule display and the word Jmol in the lower-left of the applet.
A dump of the console is attached including a backtrace showing the NullPointerException.
*Firefox (Iceweasel) 8.0
*IcedTea Web plugin 1.1.4