Seems like it's a card issue. Check to see if the card has bad sectors. May be it's time to use some genuine brand new cards. However, we have customer using the cards for 18 to 24 months and have no problems. We found Kingston also has good compatibility with the X2. Try using H2TestW as suggested by other forum members to check for card error.s
You can also try using the latest firmware 1.2.7, but I would suggest use other cards for testing first.