I have found out that when installing another carriers OS, or deleting the vender.xml you will most likely eun into the app world problem.
There is, thankfully, an easy fix.
1. Connect your device to your PC via usb, and use BDM to remove App World.
2. Visit Download BlackBerry App World
from your device browser
That's all there is to it. Posted via BlackBerryForums.com Mobile