What does it mean when my phone says "insert SmartChip?

I have the AT & T Sony Ericsson W850i and I've had it for about two years. now suddenly he came out of the text I was typing and something came up saying "insert SmartChip". I had not taken anything out or discarded if they seemed the type sampling. he would not let me go out the window I had to restart it. then it would not be back in about 4 hours. he worked for a while, but now the entry with the same message and I was not even using it right now. if anyone knows how to fix the problem I would appreciate some help. thank you in advance.

remove the battery and have a look at the SIM card. I think the SIM card just shook the place … put the SIM card again and make sure insurance in place and put the battery back inside. give that a try.

PROBLEM : Sony Ericsson “INSERT CORRECT SMARTCHIP”