Java Problems In Tiger 10.4.2


Hi,I hope you can help me.
I use a company called GCI financial to trade demo shares as a training exercise.

On Panther I have had no problems loging into my account ,since installing Tiger when the applet starts my login screen freezes up.
I get "the spinning beach ball of death" then Safari fails to respond with no other obvious option but to force quit Safari.
Is this a problem with Java?
I am using 1.3.1 and 1.4.2 plugin settings.
I also have J2SE 5.0 installed but in it's settings the runtime has 1.4.2 first in the list.
The ActForex certificate is a self signed cert and is expired but this has always been the case and have selected YES when prompted.
Any light you can throw on this problem would be much appreciated as I seem to be in grey world here with no experience of Java. (I may be doing something very stupid as usual though)
Thanks again.