Card was not being detected, so certain apps stopped working correctly. (SwiftKeyX could not auto-correct, Dropbox can't open docs, etc) You can't FORMAT the card, b/c the phone doesn't see it! So, I just removed the microSD card, and plugged it back in. No reset or anything needed. FIXED. Note, this was NOT the "paper" SIM card under the battery, but the tiny micro SD card that pops out of the side.