So far, this error is specific to machines running windows 2000 pro. IE6. The problem is NOT user specific, as it only happens on certain machines. There is no response from the zimbra interface when a user clicks "reply" to reply to an email. Internet explorer has a error alert in the bottom left corner. When double clicked it displays the following error info:

This has started to happen since we updated to the current zimbra release this past friday. Is anyone having the same trouble?

Internet explorer and Java are updated to the most current releases on these machines.