Not sure about cingular but with T-mo it can take up to 48 hours for them to provision your BB, I had the same thing no browser finally two days later Voila!
Sending service books from my BIS account and registering didnt work.
This is a problem if you did not get a data package when you signed up. You will not have the web browser. If you did sign up. You will need to set up your email and send the services books to your phone, this will force an OTA push with the links to the web, Good luck