had the same problem with my Unofficial CM9 Build,
it`s easy to fix:
in build.prop, find the line: ro.modversion=9.0.0-RC0-p990-UNOFFICIAL (near the buttom) and just delete it, and your baseband is working.
(I`ve got this info from owain94, so all credits goes to him or the person who found this out.)
I`ve just one question, (don`t want to open an other threat)
How can I get the Build Version shown at system settings -> about phone, like in owain`s Build or Nova HD Rom?
HTC One S <-Dark Jelly S Editon, (CM10.1) , (CM10)
Google Nexus 4 <- Dark Jelly N4 Edition, (CM10.1)
LG Optimus 2X <- Dark Jelly 2X Edition, (CM10)