This just started happening today and I'm not sure why. I plug my phone into my PC with the USB plug (tried 2 computers) I am prompted on the phone which USB option to use. I choose the first one "Charge Only". I go to music or gallery and it says, "SD card is in use and cannot be accessed." (The pc can access the card) I check the USB settings and it is still set to charge only, I click done (like I'm choosing USB only again) and then it proceeds to prepare the SD card. The SD card is now accessible through the android OS again. It's not causing major problems but I'd really like to know why I need to choose USB charge only TWICE to make the SD card usable again after plugging it into my PC. Also, I tried rebooting and it's the same. Update: okay, I just uninstalled double twist (only thing I installed today) and it started working like normal. Strange.