Dave, thanks for sharing your experience. I will re-examine the cards on a Linux system and see if there is anything there. However the Pi would not take my SSH so I am not optimistic.
I did read on another forum that some users were having SD cards getting repeatedly "burned up" by their Pi's, but others (like you, having lots of experience with multiple units running all the time), were incredulous. I am new at this so it is completely within the realm of possibility that this is a matter of operator error. This was indeed flashed from a Windows machine, but originally I was able to see the files on that machine, so unless the Pi reformatted the card I don't see why it would now be unreadable on the same machine.
