By any chance, did you configure your kernel to probe all LUNs for SCSI devices? Since USB storage devices emulate SCSI, and card readers show up as multiple devices, this is necessary to access all the slots on the card reader. Also, I've had some USB storage devices, like my cell phone, show up with no partitions. In that case, I had to mount the whole disk, I.E. /dev/sde, in order to access it. HTH.
