What kind of SIM do you have? If you are on AT&T you should have at least one of the 3G SIMs and not the 64K or 32K SIMS.
My N73 will no longer read my SIM card. I have tested my SIM in other phones, and tested other SIMs in my phone. As expected, my SIM is fine, but the other SIM will not work in my phone.
The N73 will just display the error "SIM card not valid." immediately after the Nokia graphic. (Before the hands even join.) The phone will boot up and work perfectly without any SIM in it.
I though of flashing the phone to a new firmware. Well, Nokia Software Update won't work without a SIM inserted. (What difference should that make?) I tried to connection to the phone via the USB cable while the error message was up, and no go. I cannot access any menus.
Is there a way I can flash without it a SIM? I have a 3 year warranty from importgsm, but they say it may take 6 weeks or so. Should I just bite the bullet and get it replaced?
I had this problem on an early firmware when I had a few bars of service, but since updating it hasn't been a problem. I'd borrow somebody's sim card and flash your phone (surely you aren't the only person on a gsm network in your area!). If your sim card is really old you should ask at&t for a new one.
used all 3 main types of s60 phones, flip, slider, and candybar.
Progression: Inno 90->6600->X800->6600->N80->N73
It's a 3g SIM, and I just got it from AT&T a little over a month ago. Non-3g SIMs did not work either.