Wirelessly posted (8800: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.0) BlackBerry8310/4.2.2 Profile/MIDP-2.0 Configuration/CLDC-1.1 VendorID/102)
Also at our FAQ site, see "How do I reset my messages" link in the first general faq section.
http://www.blackberryfaq.com/index.php/Main_Page