Used some papers to apply pressure, and worked for me. atleast for now.

I usually get this when the phone has had power issues. I suspect the communication with the radio firmware gets out of sync and it takes awhile to sort itself out. Taking out the SIM and replacing it almost always fixes it for me. For those times when it hasn't a second try always does. I don't think it's a physical thing that increased pressure helps, I suspect it's just that you're taking out the SIM, and even whilst the phone is off, the radio controller is still running as long as there is reserve power in a capacitor or some such somewhere.

Yesterday I got the same error as everyone in this thread:
"All telephony functions, including emergency calls, are disabled due to a communication error. To recover, you might have to reboot the device".

A red line crossed sign of sim card indication is shown on the status bar.

no call and internet,Wifi are not working what shal i do,
Help me please.

You can try Dr.Marcial's method : http://talk.maemo.org/showpost.php?p...5&postcount=43
But it will only be temporary...

Strange that your wifi doesn't work either, mine is ok...

http://www.jabawok.net/?p=14

Fixed it!
thanks!

only for a while I'm afraid...

I've heated the gsm chip , so far no problem ,3 weeks and counting

Lol this could be the same thing like with broken computer graphic cards: You can bake your graphic cards to get them working again, because some capillarry cracks in the solder joints will be filled up by reheating the board with ~120-250 °C.

But it is difficult to remove all plastic parts from N900's mainboard so it is maybe possible to do it locally with a hot air gun!

Yes, I had that problem too and you guys scared me to death, that the comm chip might be dead. I opened up the back cover, got the SIM out, and with the tip of my screwdriver i scratched out some lines exactly where the pins on the SIM reader should be. Scratched out a little (be gentle, very gentle, treat it like you would treat your girl) the pins on the SIM reader and voila, it works perfect.

After this fix, I even applied some pressure in key points, even shaked the phone like crazy, no more signal loss. Everything is ok. Also, my SIM is a little more slim than other sims, idk why, but it just is so on a shock like a fall on the bed it would loose signal for ~1 second, but I got rid of that error.

Here is a pic with the scratches on the SIM:

I can assure you the problem is far more complicated. I changed my SIM card twice and no change, now I even get the error message without sim card... it's only temporary (just read the others posts), enjoy using your telephony functions until the last day!