'No SIM card" message after IOS 5.1 update

Just updated iPhone 4s to IOS 5.1 and my sim card is no longer recognised. Did a restore and still getting the same message. Anybody else have the same problem?

is it unlocked or on a supported carrier

The phone is unlocked, no contracts, using one of the main carriers in Australia - Optus.

no sim error on 5.1

i have the same problem. my 4s worked fine with 5.0.1. now it says "no sim card installed". it happened the moment i upgraded to 5.1.
the same sim card is now working fine with my 3gs. please heeeeeeeeelp.

IPad 5.1 issues

Yep, same issues with my ipad2.
As soon as I upgraded, it started giving me the same message No Sim.

But over the last couple of days it has been going on and off ... Very annoying.

I live in Egypt and do not have an iPad on any contracts. I have a sim card from Mobinil which has been working perfectly for several months since I got it up until now. So I think the problem has nothing to do with operators but more to do with the update.