Just to say thanks. I got a seeeduino a couple of days ago, tried using a card holder hacked from a broken camera and couldn't get the DevicePrintDemo to work (mmc::initialize() returned 3). All the connections tested ok with a multimeter on beep but I noticed a (2k) short on one of the connections. So I took the advice elsewhere in this or parallel thread and soldered wires directly to a micro-adapter, set the + to 3v3 and it just worked - no resistors needed!!
The adapter seemed to have pin 3 connected to pin 6 internally so that saved one of the connections.