Mid-'12 Air freezes after wake up w/ external monitor attached

Every once in awhile, while I have my Air hooked up to an external display with the Air closed, the computer will freeze after attempting to wake up from sleep. I'm able to wake the computer up with my bluetooth trackpad and keyboard, but all that displays is a blue screen on the external monitor. The external monitor is a samsung and I am connecting it through a mini-display to hdmi convertor.