Post [Q] Unknown IMEI for motorola mb855

I recently flashed cm_10_20121127_UNOFFICIAL_sunfire rom on my motorola mb855 phone. But its showing "Unknown IMEI" hence i am not able to get network for GSM sim.I also tried two more roms but still not able to get IMEI. Is there any way to reflash IMEI into mobile. Please help me. Thanks in advance.