This is strange. I am also running 4.0, although this is the AT&T version of 4.0. Tmobile's 4.0 is not out yet.
I go to options > sim card. The screen now shows "SIM Card: Security Disabled". Then the ID and Phone number. With the highlight on the ID line, I hold down the <alt> key (I don't have a key specifically marked <alt> and I assume it is the key to the left of 'z') while keying in m e p d and nothing happened. I try holding down the <alt> key and <cap> key down while hitting m e p d and still nothing happened.
I know this BB is still locked. Does that make a difference? At the "About" screen, I show v220.127.116.11 (Platform 18.104.22.168)