Ah, here's something interesting:
dmesg reports this about mmc1 (2nd SD slot):
host doesn't support card's voltages
error -22 whilst initialising MMC card
it also says this about mmc2 (i thought it was just 1 and 0?), but it reports this regardless of whether there's a card in slot 2 or not:
card claims to support voltages below the defined range. These will be ignored.
new SDIO card at address 0001
Mass storage mode doesn't work. I have the correct cable now, but in order to enable mass storage, you have to select which card, and the pandora doesn't think the card exists, so it can't enable mass storage.
There is no change in the output of fdisk -l. (It lists mmcblk0p1 if it's inserted in the first slot, but never lists anything else)
How's LED activity if you put the card you use in the left slot (probably filled with some pnds) in the right slot while leaving the left slot empty before a boot up ?
It blinks once for just a moment.
My pandora also seems to have trouble with staying in low-power mode (it keeps turning itself back on), so I'm going to do a full firmware reflash and see what happens.