Small Suggestion

[grindstone]

Please tell us you're not running nvidia drivers...(only half joking). 

Sorry if you've already posted what you're running, but get us the results of each of these if you can:

Code:

inxi -G

Code:

xrandr --listmonitors

Code:

xrandr --listproviders

Code:

xrandr

Code:

sudo lshw -c video

And is this HDMI? Peek through your dmesg and see if there are more clues (like maybe firmware not loading for the approp driver or something).

Try searching upstream for screen timeout.

Thanks.