Hi, I tried to look for the same problem but mine seems to be different. I've had my own share of 4.2.1 unlocking problems/battery draining/ etc. I've restored and Jailbroken yet again but this problem still occurs. I would lose rexception (no service) have problem sending text messages and making calls. For example, I'd have 4 bars and I would proceed to send a text message or make a call, and I wouldn't be able to send a text or make a call. ANy fix for this? Possibly on Cydia? Thanks in advance.