My friend's N9 was behaving weird, he gave it to me, I flashed his with my FWs. Everything went fine for 20-25 days.. then one day his phone turned off and when turned on it automatically turned off.. we removed the SIM card, it turned on okay, no problem at all. So with SIM card on, it was turning off. I reflashed his N9 with my FWs again, but SIM card turn off error was not fixed.
Then I decided to download his product specific FWs from Navifirm (these files are huge and we don't have high speed connection.. sigh).. now I've downloaded his FWs, but failed to flash.. it says downgrading not allowed.. my FWs product code was 06, his is 05.. so this could be the issue.

Now I have 2 questions:
1. that SIM error, was it a FW problem or a HW one?
2. If that's a FW problem, how can I flash his N9 with his specific FWs?
The phone runs okay without the SIM card.. what to do? Help me..
attaching the flasher screenshot btw :/