This produces a blank png file in mint 17, but works fine in ubuntu 12:
gnome-screenshot
Opening the resulting Screenshot file in the ~/Pictures directory shows completely blank image (all black). Opening the png file with another viewer shows the same thing.
Trying the command with the -a options and then dragging a specific area also produces a blank png file in the Pictures directory
gnome-screenshot -a
I'm running Mint 17 in a virtual machine in virtualbox. Yes, Guest Additions has been run and the rest of the virtual machine operations are fine.