Has anybody experienced lately the above described problem, and maybe even identified the cause? I have bought my N9 in July this year, and a few weeks ago it started having this problem, i.e. occasional loss of connection and asking me to enter the PIN.

It would be a shame if it had a hardware issue like the N900 (my previous phone) had. See this thread:

http://talk.maemo.org/showthread.php?t=36447&page=18

Thanks in advance for any helpful hints.

It seems to be a hardware failure. It may be somehow related to broken sim card tray although faulty gsm modem better suits to problems appearing on n900s. My n900 loses signal and asks for pin quite often while using gprs/edge internet connection. It looks like nokia made n9 in the same wrong way as n900

I have the same problem. It's not a sim problem but the holder of the sim... The thing in that you put the sim not lock good... And.sometimes loss the connection....
try to put a tape on it for close...
Sorry for my english

Just get another phone. Why suffer?

I just bought the phone a few months ago.

sorry to hear that.

I had the same issue. Just make sure the sim is not playing in the tray. Put the tray in and make sure it is fitting well.

I hope its all about sim card in the tray. I've just bought n9 to replace my faulty n900

It happened to me N9 and my wife's as well and it disappeared by itself. I just made sure that everything is fitting as best as I can.

I hope it will not be a faulty hw. Good luck

Maybe sim is not deep enough to bush the button witch tells the phone that sim is there. You can cheat it with little piece of tape bottom of sim card. Sorry for my English.