Executive Summary: Stock SD Cards seem to have issues. Root cause is software based according to HTC. Interim Solution: 1. Download & Install SD Formatter from Home - SD Association onto a PC 2. Hook up Evo to PC & copy off HTC Sync, which you'll need if you wish to use wired USB tethering. 3. Use SD Formatter and FULL FORMAT the card. Interim Solution #2: 1. If the above does not work, replace SD card with another. Class 4 or higher SEEMS to be more stable.