Since I installed Freya on my PC every screenshot I take using 'print screen' key is black. I also tried using 'import' command with different options, but it only made opened windows visible on the images and my desktop was black. I had the newest AMD drivers installed from AMD website. My graphics card is Radeon R7 250x. The only solution I found on the internet was to upgrade kernel to new version and install AMD open source drivers and I updated kernel to 3.17 and installed the drivers, but it didn't help. I tried upgrading to kernel 4.0 and 4.1, but then I got black screen after boot. So now I'm using kernel 3.17 and AMD open source drivers and I still have this issue - all my screenshots appear black.
PS My display is not recognized by the system. Could this be the cause?