The following are general instructions:
When the chat files are recompiled from the source they will be named
something like wbchat.class, wbchatin.class, etc.
You should delete all files in the wbchat directory (including wbchat.zip and wbchat.cab) and replace them with the new files with the XXXXX.class files. Then you need to reset the webcrossing cache and empty your browser's cache/temporary internet files (browsers hard cache applets, just refreshing/reloading or restarting the browser is generally not enough).