My N9 had 3G connected constantly for about a day. Later, while I was downloading a file (about 150 MB), the phone turned off without any warning.
It refused to turn on after that. Thinking it needed a recharge, I let it charge for half an hour, only to find disappointment later.
Somehow it struck me to remove the SIM and then try. It worked!

So, now the situation is if I insert any SIM card (of any telecom service), the phone will start finding the network, and then immediately turn off without any warning.
However, if I insert a SIM in flight mode, N9 will stay alive. Apparently, finding the network does the toll on my phone.

I have also tries resetting as well as flashing the phone (zero flash). No gain.

Has anybody else faced this problem? Is there any solution to it (hopefully other than replacing some hardware) ?