Generally it's best to ONLY delete files off a memory card using the device for which it was formatted / written by.
On a related note, moving / manipulating files on a memory card is always risky -and if done so frequently can potentially substantially shorten the life of the card.
In regards to memory cards not reading - most often the problem is simply incompatibility (ie. different file format), but another frequent cause can be lack of power - if connecting to a computer, try using a different port, such as on the back (if using a USB card / reader adapter), since ports on some PCs (ie. front verses rear) vary in the amount of power they will pass-through.
Ron
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Domagon - Website Management and Domain Name Sales
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