SD card suddenly damaged I'm using Xperia C. My SD card works perfectly fine but after I power down my phone and turn it back on, suddenly it says that my SD is damaged and I have to format it. I can't even mount it on my phone cuz when I do, it just unmount it again. This is not the first time it happen. Last time, it was with my first SD card and now, my second. What should I do?
I just had this problem less than an hour ago on my Acer Iconia a500. I've had it happen with multiple SD cards on different devices. This is how I overcome this problem everytime. The only way that this wont work is if the card is fried

To the problem of your "damaged SD card", what's most likely going is corruption of the file system. Something on the phone made an invalid entry. 


Plug your SD card in the reader
Run Mini Tool Partition Wizard (MTPW) 
Select Partition Wizard, other is Data Recovery
Pick the SD card in the list
Right click for drop down menu
Scroll down and click on Check File System 
Let it finish, then exit MTPW
Unplug and re-plug SD card into reader
When "Do you want to scan and fix" pops up, check both
When finished, unplug from reader
Mount in your phone and enjoy. 


I know it's a late answer,  but knowledge is power.