BTW, I am using sun JDK 1.6.02
See http://www.jboss.com/index.html?module=bb&op=viewtopic&t=96755 . The instructions I give there work for 4.0.5 as well as 5.0. beta1 (in 5.0 beta2 the web console is hopelessly broke). Also, I think that using JDK 6 is only asking for more problems (you are getting a different missing class).
Peter, thanks for the suggestion.
I tried ur trick, i.e. unpacking Applet.jar and placing the unpacked content at appropriate location. But it did not work and the error is same.
Then I tried with JDK 1.4.2. But still the result is same.
Do what I do: ignore the Web Console. It is mostly useless anyway because it has not been updated in ages. Besides, configuration changes made in the Web Console disappear on the next reboot. If you want to configure things, edit the XML files.