My brand new 32GB SanDisk SD card had a very high rate of data corruption in my Droid 4. The card worked perfectly, until I use it in my Droid 4. So...The reasons I think this is a compatibility issue are: I tested the 32GB SanDisk SD card extensively (20+ hours) separately, in an SD card USB converter, and with multiple check-disk programs. 0 errors, clean surface. Before the SanDisk, I used a 4GB Kingston SD card, also Class 4, which never had any corruption issues. I searched Google, and other Droid 4 owners are reporting similar SD card data corruption problems. Problem: I bought a Sandisk 32GB MicroSDHC/SD Card, Class 4, and started getting errors as soon as I put it in my Droid 4. I would transfer apps via my USB cable, and the files would look OK in the phone's file manager, but when I tried to open or run them, they would do 1 of 4 things at random: Error, just disappear, go from their normal size to 0kb & not open, or work for a few seconds but then error/close.