No Service - iOS 5.0.1 and 5.1 - BB 05.13.04

Hi all,

I have a 3GS with the new bootrom. In late december I would have jailbroken and unlocked this phone and it worked perfectly till now. I have bought a new one so I am trying to install 5.0.1 on it again. The only problem is that I keep getting a no service with me sim card.

I have tried 5.0.1 and 5.1 with ultrasn0w 1.2.5 but no luck. I have even tried installing the ultrasn0w fixer for 5.1 which does not help.

So what has changed as I have had a working phone for 4 months but now not?

Thanks in advance.