That's just plain out strange. The difference between Class X and Class Y is internal to the SD card and the only thing the SD Host cares about is the version of the SD controller on the card. The card could have been defective, or had an internal short causing it to sink too much current from the slot. Either way, have you tried to see if the SD card still works in any other devices/readers? If the PE's SD slot still works, and works with another card, then process of elimination points to the SD card itself.