What version of the Mac OS does this user have? 10.4, 10.5 10.6 or ?
It's some iteration of Snow Leopard - 10.6.4, I believe.
Got a call from the customer having the problem saying he just upgraded to the latest version of Java for OSX today (it was released yesterday), Java SE6 version 3, and the problem disappeared. Too bad that the integrity of the FMP runtime is so dependent on which version of Java is installed on any given machine, but glad that the problem got solved. I had no idea myself what to suggest.