I've had this problem for a few releases and it affects all of my laptops; I specifically have this issue on an alienware m14x, a lenovo ideapad y530, and an acer aspire 4720z. If I unplug the external monitors or use pm-suspend the system suspends properly, otherwise it will just turn off the displays when I close the lid or click suspend from the menu bar. This problem is nonexistent when using Mint(kde, cinnamon, and mate). It is also not an issue with Unity itself as I have the same problem with kubuntu and lubuntu. Does anyone have a solution?