I have a 27" iMac (one year old), running Lion. I just bought an 8Gb Sandisk Micro SDHC card and a friend gave me two adapters, one which allows me to use the SD card slot, and another which allows me to use a USB socket. My problem is, they don't. Plugging in to either and nothing shows up in Finder or Disk Utility. On the assumption my machine should be able to read and write to these cards, is there anything I need to do first, or maybe I just got a faulty card?