Default [Q] Null IMEI and EFS backup

All of sudden today, the voice calling service on my phone stopped working.
It gives the BSOD whenever I try to make a phone call...

I was on CM11, then I tried to revert back to stock, but still the same.
Strange thing is that the SMS and mobile data is still working fine.
The phone connects to the network service fine. (I'm on Straight Talk.)

Just can't make or receive any phone call...

I found out that the phone's IMEI shows "0" so thought the issue I had must have something to do with the null IMEI.

I knew that I had EFS backup (it's about a month old), so I tried to manually restore them (all 3), but the result is the same..

Now, I don't know what to do.. Can anyone help me out?

My Smartphone History
iPhone (1st Gen) >> Samsung Galaxy Spica GT-I5700 >> HTC Nexus One >> iPhone 3Gs >> HTC HD2 >> LG Optimus LTE LU-6200 >> Samsung Galaxy Nexus GT-I9250 >> iPhone 4s iOS7 >> Samsung Galaxy S3 >> LG Optimus G E970 AT&T

My Tablet History
iPad (1st Gen) >> the New iPad (3rd Gen) >> Samsung Galaxy Tab 2 GT-P3110 >> Samsung Galaxy Tab Plus GT-P6200 >> Nook HD+