If the box goes straight from 102 to 106 then the card isn't being read properly. Go to Services -> 4 -> 5 and see if the viewing card number is showing. If it isn't then (assuming it is a valid card) try withdrawing and inserting a few times in case the contacts are dirty.
If the serial number is showing then I really don't know. Try your card in another known working system and similarly a known working card in your system. This might give some clues.
How suddenly did this problem occur?
Is it possible that the card is in the interactive slot instead of the card reading slot?
PaulR