So long story short, you've probably lost your IMEI. You can check this by going into Settings -> About Phone -> Status then scrolling down to IMEI. If it begins with 044 or something similar then you know you've lost it.
So to solve this:
1. Flash back to the stock Gingerbread you were on by means of Odin, there are many guides for this but the one http://forum.xda-developers.com/show....php?t=2444308
is quite comprehensive (and leave the OP a thanks as well)
2. Download CM9 from the Cyanogenmod website.
3 Root your S again (this will depend on which Gingerbread rom you flash).
4. Boot into CWM recovery. Do the usual data/cache/Dalvik wipes.
5. Install CM9. Let it boot. You don't need to download ICS gapps for CM9 as all you need it to do is boot.
The reason why you install CM9 is to make sure that the IMEI sticks when you then flash a JB rom. Flashing straight to JB from GB tends to lose the IMEI as said before.
6. Once you've let it boot, reboot into recovery again. You don't really need to do the same three wipes again. Install CM10.1.3 RC2. You'll need to flash the zip a few times- three times at least. Flash Gapps as well, of course.
That should hopefully make your signal reception and GPS work
(I covered this quite briefly so if you do need clarification on any of the steps don't hesitate to ask)
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