hello me as well
i JB with blackra1n (not too sure which one, not the most recent RC3 release, but for the uptodate 3.1.2(?) firmware)
i get the message that i'm not subscribed to a celluar network, even though i can see O2 and 3G on my phone.
in the past it usually happens when i install something from cydia. so now i do a pre-sync and back up before i install anything from cydia.
i intsalled anyring (which installed Rock), and some dictonaries from cydia last night. i didnt like them so i uninstalled them. and i thought everything was fine, but i cant get any internet from the 3G on my phone. so i'm going to go home an restore from back up.