I have the exact same problem, anyone with any kind of possible solution? Here's what I tried already:
1. Removed both battery/SIM for a minute or more then rebooted. (Also made sure that 2G was off)
2. Called a Koodo tech guy who updated the SIM.
3. Went in store to try and put my SIM in a different phone, SIM worked fine.
4. Lady tried installing a different SIM card (her own), still same problem. Tried a brand new one, still not working.
5. Backed up my pictures and factory reset the phone. Same problem.
6. Took SIM out, and the phone does recognize there is not a SIM card and now the phone gives me the NO SIM CARD message at unlock screen.
7. Updated to 4.3 - Nothing changes.
8. Browsed the internet for hours then cried myself to sleep, hoping someone would help me out eventually.