Sorry for the vague question.Probably something with the baseband I guess?
Update your baseband to the march 11/2012 baseband. All roms switched to support that and it isn't backwards compatible. Check xda-developers.com for a how-toSorry for the vague question.
On cm-7.2.0 stable+ and 050 stable (+betas preceding stable) audio/phone is not working. If I make a call from the cellphone I cannot hear anything, if I call the cellphone it doesn't react in any way, nothing on display and no ringing.
I went back to rc2 and b9, combo is not perfect but at least I can make and receilve calls.