please make sure the memory card is inserted correctly, remove the memory card , and reseat it again in place just to make sure .
if the card was removed during an ongoing operation this may have corrupted the card, try to read the card on a computer with a card reader to test it.
the G symbol is shown when the packet data connection mode is set to "always online" and packet data service is available. you should change that to "when needed" through:
menu > settings > connectivity > packet data > packet data conn. > make sure that this is set to "when needed".
Fear not those who argue but those who dodge