Android phone file structure seems corrupted when connected via USB
I'm not sure about doing this on a Mac, But if you have a windows PC, preferably a windows 7, try the following:-


Connect your phone via USB to the PC with the SD card. Turn on file sharing.
Go to My Computer, find your SD card "drive", right click > properties.
Go to Tools tab, under "Error Checking", click on "Check Now".
Any SD card related file system errors should get automatically fixed.