Thanks for the reply

ls /dev/mmc* shows three listings -

/dev/mmcblk0
/dev/mmcblk0p1
/dev/mmcblk1

I imagine a formatting problem could have been an issue for the internal one - but the external ones should be fine...

The card worked fine in my digital camera, so it definitly works - formatting could be an issue for that though then, no idea what the camera formats to.

I don't know when this happened, I didn't have any files stored on there at the time that i miss, so don't know if anything in particular screwed it up.