There are SD card images
here. Use the eSATA images, or the newer
all images, but for an eSATA plug you must set arcNumber to 2678 in order to use the
all images.
SD cards can go bad; they experience wear and do not have infinite lifetimes. You could try booting from NAND, mount the SD card, and investigate / fix the problem. Certainly you can upgrade the kernel that way.