Had the same thing yesterday, tried all sorts of modems, with no avail.
Ended up flashing a stock rooted Rom (MGA), flashing a custom recovery and restored a Nandroid. Forgot that flashing a complete stock Rom usually also wipes the internal SD so that was a bit of a hassle.
Now, running a new Rom again, with Wifi, sound and being able to make/receive calls again. Easiest fix also: flash a (compatible) stock Rom
So, everything works now. The short version for other guys with the problems is:
- flash stock rom via Odin (PDA)
- you can find the stock rom for your country at sammobile.com
- also use the "pit-file" of the linked post (but I don't know, what the pit-file is changing?!)
- re-root your device again, because now it is not rooted
- new custom rom
Thanks for every help!!!