bro.. let me add some more info to this thread....
extract from
http://support.raidersoft.com/resolve.html
Resolving Common Problems
1. My web browser reports "load: class Client not found" error when loading SigmaChat, ICE, or RaiderCSS
The Load class Client not found error is among the most notorious of Java applet error messages, and can be caused by a number of different problems. Usually, this problem indicates that your web browser has downloaded/ cached an invalid copy of our chat software (cache instability or an error in download). Minor network glitches between your computer and RaiderSoft's servers can also cause the problem. Ninety-nine percent of the time, the problem can be resolved by emptying your browsers cache (or Temporary Internet Files), then shutting down all instances of your web browser, and trying again. In rare circumstances, a reboot may be required.
To empty your browser's cache using Microsoft Internet Explorer:
Click on Tools from your browser's main menu.
Select Internet Options
Under the General tab, click Delete Files... in the Temporary Internet files section.
Important: Shutdown all open instances of your web browser.
To empty your browser's cache using Netscape:
Click on Edit from your browser's main menu.
Select Preferences
Select and expand the Advanced category.
Click on Cache
Under Set Cache Options:
Click Clear Memory Cache
Click Clear Disk Cache
Click OK
Important: Shutdown all open instances of your web browser.