Re: 295.33 unreadable display after resume on external monitor via displayport 2560x1
I debugged something that sounds similar, but it's not related to how long the display is asleep. Rather, it's random whether or not the problem will occur. Does the problem go away if you run "xset dpms force off" and then hit a key or move the mouse to wake it back up, repeating those steps a few times?
If so, then it should be fixed in a future release.