No signal on custom roms (SGS2+) I have a Samsung Galaxy S2 plus and rooted it via Odin and put CWM on it, with which I installed the unofficial Cyanogenmod ROM and later P.A.C. 
Unfortunately I had massive issues with the signal: Despite the fact that the sim gets unlocked when entering the right sim pin at start, there were always only emergency calls available. When trying to manually select the mobile service provider and selecting the available networks (Wireless &amp; network->More->Mobile Networks->Mobile Service Provider), there is an error while searching, and when telling the phone to automatically select a network, it says registered in network, but there is still no connection.
Really odd is the fact that when activating the option '2g networks only', the phone is registered in the network of my mobile service provider, but quits after a few seconds.
I got the phone from my MSP, so it's branded. May that be the cause of my problem?
I also noticed that both the Cyanogenmod and the Pacman ROM use the same kernel: 3.0.31/skullface@Ubuntu_13.04#1. This one is from Cyanogenmod.
Any help is appreciated.


P.S.: Some terms I used may be incorrect because the language on my phone isn't english.

EDIT: I found out that the problem has something to do with a possible netlock on my device, because it askes, when there is the pin code validation disabled, for a code to unlock the sim network. At least that was what some forum threads were suggesting (in german, so I won't post them here).
Normally, this behaviour thus shouldn't occur, because I use the same sim card I used with the stock rom. May it be that my EFS directory is corrupt? (the one which contains the IMEI and stuff)

EDIT: I think one needs to flash the modem, which is possible for example with ODIN. Haven't tried it although.
FYI, I found out what the problem was: The stock rom needs to be updated to 4.2 (you can get the official rom here if there is no update available), I think because of the bootloader.