I’m not exactly sure what they are having for a problem. Sounds like their browser isn’t loading a needed file for the java applet.

What browser version are they using?

What Operating system are they using?

Users of Mac computers (apple products in general) may or may not have problems based on operating system and browser used.

Best browser to use for chat is Internet Explorer 5.0 or higher, 6.0 recommended.

Also, did they check “yes” when the popup window displayed the request to allow the applet to run? This is called the digital certificate and if they said no it will cause problems. If they did do this tell them to clear their cookies and temporary internet files and try again.