I think i know what is wrong.
If you want it to show as Mass- storage right click the button next to the track ball once you plugged it in as USB mode. click yes. Go to properties. Make sure your File system is set as FAT. Last time my memory card did not show was because it was set as FAT32. nonetheless re-format and make sure its FAT take a picture on phone if memory card is working you should get a option to save it to your memory card.
If thats not it got on phone
options
advanced options
media card
and make sure its on