Do two things, one of them will likely fix it.
Go to Options > Advanced > Host Routing Table. Click to Register Now.
Go to your BIS website at TMO (see link below) sign in and go to support for your phone, and click Service Books > Send Now. Main Page - BlackBerryFAQ
Pull the battery on the 8100 and let it reboot. You should get a welcome message from TMo, and heopfully your browser will work.