Im using a Sharp Zaurus SL-5600 and I have a problem with an MMC card. It is a Transcend 64MB card. It worked the first time I used it but now it does not mount, nor am I able to format it. I have tried everything I can think of, but it does not work. I have tried mkfs.ext2 /dev/mmcda1 and dd if=/dev/zero of=/dev/mmcda1 (count=62720).
fdisk /dev/mmcda returns a cannot read error. Please help!!

I was hoping someone else with a Z might try and answer this one, as I have yet to corrupt a SD/MMC card on my Z, but a couple of things to try.

My 5600 doesn't seem to like it when I use /dev/mmcda to access the card, try using /mount/card instead. Might make a difference, then again it might not.

If you have any other devices that can format a SD card, like a card reader or a digital camera, try formating it back to FAT16/32. Some of the cards flake out when they're formatted as ext2.

If that doesn't work, I'd return it. An SD/MMC card shouldn't bite the dust after 1 usage. Try a SanDisc card. I got a 256Mb card that's been working pretty good over the last couple of months.