Got to mention this as it's happened a few times,
are you inserting the cards the right way up,
some card readers differ that way.
hmm, its weird that the USB port is working otherwise id suggest finding the 7-pin for the memory card reader on the motherboard, although you could try taking it out and putting it back in see if that does anything, it may reinstall the driver and it may work
I have the exact same problem, i put any card into the reader, the yellow light turns on but nothing comes up..
go to windows and type in 'partitions' there should only be one option, open this, and then scroll down to see if there is your memory card, if its there then it may be hidden from my computer, so try and find 'unhide' or something similar