Comment 52 for bug 712075

I had exactly the same problem. The solution that worked for me follows.

THE PROBLEM :
The symptoms:
* the screen flashed every 10 seconds.
* X won't run in a resolution higher than 1024x768 , while it used to run at 1280x1024.
* missing virtual terminals under ctrl-F1 t/m ctrl-F6 keys. There isn't just anything to see.
It looks like the monitor isn't receiving the right timing signals.
* Every 10 seconds syslog receives many times error messages like this:

Jun 16 17:51:27 titan kernel: [ 2082.185618] [drm:drm_edid_block_valid] *ERROR* EDID checksum is invalid, remainder is 128
Jun 16 17:51:27 titan kernel: [ 2082.185627] [drm:drm_edid_block_valid] *ERROR* Raw EDID:
Jun 16 17:51:27 titan kernel: [ 2082.185635] <3>35 30 36 31 35 30 36 31 35 30 36 31 35 30 36 31 5061506150615061
Jun 16 17:51:27 titan kernel: [ 2082.185641] <3>35 30 36 31 35 30 36 31 35 30 36 31 35 30 36 31 5061506150615061
Jun 16 17:51:27 titan kernel: [ 2082.185647] <3>35 30 36 31 35 30 36 31 35 30 36 31 35 30 36 31 5061506150615061
Jun 16 17:51:27 titan kernel: [ 2082.185652] <3>35 30 36 31 35 30 36 31 35 30 36 31 35 30 36 31 5061506150615061
Jun 16 17:51:27 titan kernel: [ 2082.185658] <3>35 30 36 31 35 30 36 31 35 30 36 31 35 30 36 31 5061506150615061
Jun 16 17:51:27 titan kernel: [ 2082.185663] <3>35 30 36 31 35 30 36 31 35 30 36 31 35 30 36 31 5061506150615061
Jun 16 17:51:27 titan kernel: [ 2082.185669] <3>35 30 36 31 35 30 36 31 35 30 36 31 35 30 36 31 5061506150615061
Jun 16 17:51:27 titan kernel: [ 2082.185675] <3>35 30 36 31 35 30 36 31 35 30 36 31 35 30 36 31 5061506150615061
Jun 16 17:51:27 titan kernel: [ 2082.185679]
Jun 16 17:51:27 titan kernel: [ 2082.284563] [drm:drm_edid_block_valid] *ERROR* EDID checksum is invalid, remainder is 128
Jun 16 17:51:27 titan kernel: [ 2082.284572] [drm:drm_edid_block_valid] *ERROR* Raw EDID:
Jun 16 17:51:27 titan kernel: [ 2082.284579] <3>35 30 36 31 35 30 36 31 35 30 36 31 35 30 36 31 5061506150615061
Jun 16 17:51:27 titan kernel: [ 2082.284585] <3>35 30 36 31 35 30 36 31 35 30 36 31 35 30 36 31 5061506150615061
Jun 16 17:51:27 titan kernel: [ 2082.284590] <3>35 30 36 31 35 30 36 31 35 30 36 31 35 30 36 31 5061506150615061
Jun 16 17:51:27 titan kernel: [ 2082.284596] <3>35 30 36 31 35 30 36 31 35 30 36 31 35 30 36 31 5061506150615061
Jun 16 17:51:27 titan kernel: [ 2082.284602] <3>35 30 36 31 35 30 36 31 35 30 36 31 35 30 36 31 5061506150615061
Jun 16 17:51:27 titan kernel: [ 2082.284607] <3>35 30 36 31 35 30 36 31 35 30 36 31 35 30 36 31 5061506150615061
Jun 16 17:51:27 titan kernel: [ 2082.284613] <3>35 30 36 31 35 30 36 31 35 30 36 31 35 30 36 31 5061506150615061
Jun 16 17:51:27 titan kernel: [ 2082.284618] <3>35 30 36 31 35 30 36 31 35 30 36 31 35 30 36 31 5061506150615061
Jun 16 17:51:27 titan kernel: [ 2082.284623]

I tweaked the Xorg.conf and tried many things, until I got nothing visible at all. Then I needed to reboot into rescue mode, and still got 1024x768 video and no virtual terminals. I tried understanding where the script in #48 could help me and got completely lost.

THE SOLUTION : After reading message #49, I halted the computer, switched off the monitor and I disconnected the power cable of the computer and the monitor for about 10 seconds. After that I rebooted and everything ran fine! I got 1280x768 resolution, the flickering has stopped, got working virtual terminals under the function keys and no EDID checksum invalid messages anymore.

My guess at this, is that there is some kind of memory corruption in the monitor or a bit has flipped. The monitor interface gets read by the video driver in the kernel and it doesn't know how to handle that. It barfs on it and somehow screws the resolution up. The only way to clear the memory corruption is to disconnect the monitor from the power net. In my opinion the only bug here is the kernel puts to much trust in what is it reads from the monitor.

Laptop users, try to remove the battery for a minute.