Comment 28 for bug 1173557

I've been having the same problem. I thought it was my KVM at first, but after some experimenting I found it's unrelated. I am able to "recover" from the error, however.

Most of my log files look very similar to Bernhard's, so I won't post them unless requested. I will try to describe the situation a bit more thoroughly, though, and my solution, because I feel it might shed some light on the root cause.

My set up is a little different than most. I have a DVI/USB KVM that is plugged into my "main" display, which switches between my Ubuntu 13.04 Shuttle XH61-V box and a Windows 7 gaming desktop. I also use an HDMI-DVI cable to plug in a second monitor to the linux box. The linux box is on 24/7. The problem occurs typically after recovering from the monitors having been turned off automatically after the set time, either over night or after I've been on the Windows side a bit. When bringing it back up, the main display is "on the fritz." It flashes as if it's out of refresh rate range, or the colors are clearly displayed wrong and have severe video artifacting. I can ctrl+alt+F1 to go to terminal, and if it was out of range it's typically back to video artifacting but sometimes stays out of refresh rate. Going back with ctrl+alt+f7 brings me back to out of refresh rate. On a whim I unplugged the DVI from the KVM and plugged it back in. Going between C+A+F1 and C+A+F7, F1 is a terminal as I'd expect but F7 is all black. This forces everything onto my second monitor, though. Going into System Settings and selecting Displays forces a refresh of the monitors and my main monitor is back. I don't even have to "accept" it, it's just back up.

Unplugging the monitor cable from the computer or the KVM has the same results, so I'm quite sure it's just a matter of forcing Xorg to drop the monitor, plug it back in and force it to rescan for it and the problem's "solved." Clearly, it's not an elegant solution. It only occurred to me typing this up, but I'm gonna try disabling the "turn screen off when inactive" option in Brightness & Lock settings to see if it's directly related to that or not. I never really noticed it was after waking the monitors back up before, so I imagine that's the real problem.