I'm on a 4s, JB on iOS 5.0.1 and "Exchange Unlock" is working fine. I do have to make sure my phone is not tethered when I boot it up. If I boot untethered the phone asks for my exhange password one time when it boots up and does not ask again until next time I have to power the phone back up from a cold boot. If I boot while tethered, the phone does not ask for the password at all when it boots, but then I have no access to any email accounts or previously entered WIFI passwords. If this happens, just untether, reboot, and all is well again.