For some reason my N900 will periodically enter a state where the cellular connectivity icon in the status bar is changed to a "no sim" icon. Rebooting sometimes fixes it, other times I have to pull the battery and remove/replace the SIM card.

Anyone know whats up? Is my N900 dying? Do I need a new phone? (which would have to be the cheapest possible phone I can get my hands on given that I dont have the funds to buy a replacement N900 or anything else that respects my freedom and gives ME control over the device)

Evaluate this fix:
http://talk.maemo.org/showthread.php...hlight=gsm+fix

bend inwards the sim tray and use a piece of paper size of the sim card .

I had constant problem with sim and losing cellular like every minute. At last I spat on my sim and rubbed it clean with my sleeve. Then I bent the metal nails/fingers that touch the sim to give them more pressure. After those have had no connection problems - except while I now write this it happened again. Darn.

Try cleaning it will alcohol and maybe back up with bkup menu then restore it. It happen to me but was gone after cleaning.

x

Can I backup sim and restore it? Or just sdcard? Never thought I could back up sim with a phone.

^ no, you can't back up a SIM card (but you can back up contact data stored on it).
But you can get a new one from your provider. After a few years of swapping around various phones it might be advisable.

The pins creating the contact to the phone can also be covered by patina; just bending them (careful!) might not be enough. Scratching the patina off might be required.

You may try all that (bending/cleaning; spring trick; oven heating) but in the end it wilk hapoen again. This is -beside the well known USB fall out- the most happening failure of this device.
It happened to me all 2-4 years of usage. And I have three of them stored away and one (which is not that bad but probably same as yours) for nostalgy still charged and reachable...

--edit
SIM change will most probably not solve this

Not sure if I can get a new sim. I use prepaid and there are some limitations with them. But have to check that.

Sounds like a high resistance which you could temporaly improve and solve...but it will happen again here the explanation:

I would say you made pressure to the back of the pcb board by cleaning the sim slot und putting back the sim.
After that all seeming ok but then you made pressure to the front of the pcb by typing on the keyboard, all went bad again due to a half broken connection and high resistance.

This could be an explanation and it is known that the N900 keyboard design is not good for the pcb and heavy typing will lead some day to this problem.
So probably you have now bad balls under the modem or some broken wires or vias in the board. If it is only the modem then it could be resoldered, when it is the pcb board you need a new one.

I think you will also have a higher battery consumtion and you would be able, if activated, to see many kernel messages from syslog regarding the modem.
And the behavior will get worse by time of usage.

My tip is try to avoid using the keyboard when it is not really necessary needed so when your at home do the console work over ssh.
Or for you as an artist and good in handcraft you could design a new keyboard, stabilize it or protect the pcb from pressures.

Source another N900 as long as you can

Edit: Also swollen batteries are PCB killer and old batteries could also play a small role for the modem.