How to fix "Invalid IMEI " after Factory reset?

The question is simple "How to fix "Invalid IMEI " after Factory reset?"
After factory reset my phone starts showing "Invalid IMEI" on both SIM slots and I can't call or to being called.

The phone is A738 with Android 2.2.1 and CPU chip is Media Tek MTK6516 416MH

Hope that information is enough.

** UPDATE **

This is the phone

Answer

I found a good solution:

DO IT AT YOUR OWN RISK

1. Need to root the phone - I use z4root


2. Install Root.Explorer (in the archive)


3. Using Root Explorer you must replace (maybe you will need to press "Mount R/W" on top right corner of the program screen) .modem.img from the archive to this location of the phone /etc/firmware/.modem.img (do not delete the old file !!! replace it!)


4. Set permissions for the .modem.img file to rw-r--r--


5. Restart the phone and maybe will be OK, but if it is not go to next step


6. IMEI information is stored in /data/nvram/md/NVRAM/NVD_IMEI/MP0B_001. Maybe changing of your original IMEI is not good idea because it is against the law but if you don't have copy of that file BEFORE the factory reset you can use temporary IMEI file located in the arhive.

The archive with files needed