>I'm having a problem when I'm login to UT. The message "More than 400 messages" is displayed. The top toolbar number remains as 0 all the session. How can I see only new messages from my last visit to this new visit and have messages at the top updated?

You have your account defined having "Automatic reset of new messages" set to OFF. This means, it requires a manual click on the refresh icon of each forum to reset the flag. If you check the related forums for that option, this will be done automatically everytime you login or refresh to get the new messages.