I agree that it's a problem on RIM's end. Two 9800's, a 9810, and a 9900 on AT&T all running data like molasses, although email and BBM are running as fast as ever.
Not sure why carriers didn't warn customers about it, but seems that there was an issues with the BIS connectivity causing the delay when opening the browsers in the BBs. I was having the same situation with my device.
I've tried to reinstall the OS 7.1, only worked a couple of minutes then back to square 1. What should I do people?
The last post here was 5 months ago, and the issue then was BIS. My suggestion is a new thread, and some better details, so that the community may help you.