I'm having a very similar problem, I have an SD card that does work, a 2gig SD. I have tried 3 other sd cards, a 1 gig SD, a 2 gig SD, and an 8gig SDHC. All three of those cards cause weird problems. It doesn't read any if them, anything that tries to read from it crashes. df hangs, du hangs, ls shows /media/mmc1 as empty. There are devices for it but it looks like it can't read it. sfdisk -l also hangs. And in order to fix any of it I have to hard shutdown by removing the battery because none of the hardware buttons work, not even the power button. Anyone have any idea what might be wrong?