A few days ago, my sd card became unusable. I tried to copy a few mp3's from my laptop (win 7) to my phone (Samsung S2 plus, running android 4.2.2) and the load bar didn't even move an inch. Eventually I got an error saying "This file cannot be copied. 1) Try again 2) Abort".
The most annoying part is that I backed up and deleted all files (to clean the sd card) an hour earlier, and now nothing works. I tried writing files using usb cable over both MTP and camera mode, without any results. I tried apps on the phone, and still the same error. The sd card is inserted correctly and does not appear to be damaged.
I have heard about the kitkat not being able to write files to sd card (like this forum post) but I think that is only for android 4.4. I have been running 4.2 for a while now, and have never faced this issue before. Phone works perfectly except sdcard.
EDIT: My phone actually tried to launch a software update, but since I wasn't connected to a WIFI nothing happened, no loading bar and no update was started.