java applets not working

Java applets do not work in Ubuntu 9.10 with Firefox 3.5 browser. I tried uninstalling icedtea6-plugin but still not getting Java applets to work. My system does have the sun-java-6jre package installed. The applet I'm trying to load does work partially sometimes, sometimes it doesn't work at all. Sometimes the applet hangs up on doing a search function. I tried accessing the same applet on another computer using windows xp and it worked perfectly on the windows computer.