I had the problem where my SIM card wasn't being recognised any more, even after reflashing etc. I suspected it was the SIM card holder as there was quite a lot of flex in it and the problem appeared to be sorted by putting squares of cardboard between the simcard and the battery.

However, I see no reason why I should have to do this on a phone with a warranty, so I sent it off for repair under warranty and a new unit has been sent back