Go to this site and download a program called SD Formatter 2.0 for SD/SDHC. It works with microsdhc cards, especially the one's that seem dead. It has brought some of my cards back from the dead. Once you format the card with this program, you might even see you EVO work a little faster and the card will work faster.
Here is the link:
http://www.sdcard.org/consumers/formatter/