Has anyone had a problem with memory cards switching the file from EOS to EKS?

[windsails]

My camera memory cards have suddenly switched from an EOS file to an EKS file and are no longer readable.  I don't know if the problem is my computer, my card reader, my memory cards, or my camera.  It doesn't seem probable that two cards would become corrupted or go bad at the same time.  I have two large capacity cards and two new high capacity cards that I haven't tried yet, but I'm afraid to try to use any of my other cards until I know what is going on with these two.   The camera I'm using a 5D Mark II.  Can anyone please help!   This is a serious problem for me! 

Thank you to everyone for your help and assistance!

Best regards,

Windsails

[windsails]

I can attest to that!  It had me going for a while...  Thanks for your help!

[hsbn]

#1 rule is always format your card in the camera. Other OS system can ruin your card format. Is your corrupted card larger than 128Gb? What do you mean EKS file?, is that the extension of your image now? Can you view your image in the camera? From your information, I can only guess that you are using 128Gb or larger memory card. With large card like that, normally the camera will format it as exFAT instead of FAT. And not all card reader/OS can read exFAT format well. Other than that, we would need more information.