I posted this on the arch forums but don't know if it's a problem with lxde or arch. I'm running archlinux lxde 64bit.
I'm using the 'xrandr --output eDP1 --off' and 'xrandr --output eDP1 --auto' commands to turn the screen on and off using hotkeys via openbox.
Here is what a screen looks like before turning it off:
And then this is what it looks like after turning on:
Also I have to kill some applications because they crash:
And then I can't access the desktop:
I've tried several variations of xrandr like specifying the resolution and refresh rate but it doesn't make a difference. I had this exact same setup on Fedora 20 LXDE and I was able to have the screen turn on and off without any disruption so I don't know why it would be different here.
I've noticed everytime after turning the screen back on that pcmanfm hangs and I have to kill it, which I think is the source of the desktop session errors. Don't know why turning off the screen would mess up pcmanfm.