From the thread here:
Now this doesn't solve how to set it as a default but I hope it helps people get the browser. I never found a way to set it as a default on my 7100. Which browser could be selected two ways:
1. Which one I launched from the app menu.
2. Which bookmark I chose and where it was filed - see Barjohn's list below.
I am not sure what controls clicking a link? Anyone?
My Web Browser Icon Is Missing!
This can happen if you've upgraded your BlackBerryOS, or if you delete your service books. This is the most common step to fix the problem via your BlackBerry:
Options Icon -> Host Routing Tables -> Register Now
Help! My Web Browser Still Didn't Show Up!
If the above instructions failed, try stepping through these instructions one by one
Try getting your service books retransmitted.
a. Login to your BlackBerry Web Client (BWC/BIS) site.
b. Click "Profiles" (At the top of your BWC webpage via your PC)
c. Click "Send Internet Browser Service Book"
Try rebooting your BlackBerry by removing and reinserting battery.
Make sure you are running BlackBerryOS 4.0 by checking:
Check Options -> About
If you are not running at least Version 4.0, you need to download and install BlackBerryOS 4.0 then repeating all the above instructions again.
If that does not work, and you are on a BlackBerry Enterprise Server (BES), try re-activating your BlackBerry on BES. This may be as simple as connecting your BlackBerry to your PC and synchronizing your BlackBerry while Outlook is in ONLINE mode.