download failed due to unknown error

When I try to download music or a picture I get a thing that says download failed due to unknown error. It also affected my camera. I got the camera fixed but can't figure out this error. I tried everything! I forced stopped the download app and restarted my phone a couple of times and cleared the cashe, history, and cookies on Chrome. It temporarily fixes music downloads and have had a problem with the camera saving pictures ... It won't even save screen shots... And I have a bunch of memory in my SD card and on the device. I also can't share external on facebook. Help?!