I had the same problem with not being able to change my broswer and subquently not being able to use blackberry maps or get to mobile.blackberry.com.
googled it and found that with my carrier (tmobile uk) you need the right service books for it.
so, i phoned them and told a tech guy (not customer services who made me change my price plan! luckily i got that cancelled) what the problem was and he said, although they should come with the correct settings, sometimes they dont.
So call your carrier, make sure u talk to a technical center guy and they should send the right stuff and in about 15 mins it should work fine!
Also ask for login details for the Blackberry Internet Service for self service. You'll have a username and password so that if you do lose BB data abilities and/or any other related items such as Browser disappearing then you'll be able to re-send the service books yourself without having to wait for other folk on the line doing it for you.