|Possibly a different standard of card. Presume what you are talking about is an SD card and not a SIM since the latter is the thing that makes a mobile phone work and there would be no reason for you to have one in a camera.|
Now as far as SD cards are concerned the older cards can be read in both old and new cardreaders but the newer cards which are labeled SD HC can only be read in a reader that is HC compliant. I suspect that is your issue. Check the type of memory card. I have just ordered a new cardreader for this very reason. My current one is a few years old and cannot read SD HC cards but my new phone came equipped with micro SD HC card.
Goin' Fishin' (Some day)