Major Outlook problem

Please help. I have been successfully running XP PRO with Office 2003 and OUTLOOK as my mail client for sometime with no problems. All of a sudden when I click on MAIL and then on either READ OR NEW nothing happens. There is no way for me to get into OUTLOOK. I have rescanned my PC for a virus and it is negative. I run Norton and Zone Alarm. My IP is Comast Cable and am able to get my E-Mail that way. Any hints, advice or fixes will be much appreciated.
Thanks, eddie460