not running applet

I am trying to log to this page: (i allready
have a certificate that it requires) The page requires java 1.4.1 by force.

when i browse through the ISA server 2000 SP2 FP1 i get the message in the
status bar 'subprogram applet_secuencia notinited'

When i browse through a dial-up conexion (without the ISA server) in the
same computer i can log in fine and use the page perfectlly so i suppose
that the problem should be in the ISA server.

Can somebody tell what is wrong and how can i fix it. I dont have to much
experience in isa server so i need detailed instructions.