[TriLUG] DisplayPort monitor won't wake from sleep

[Wes Garrison via TriLUG]

I've set up a couple of Debian boxes for my kids, and one of them has a
WQHD monitor that won't wake from sleep.

The computer wakes from sleep just fine, but the monitor "wakes up", says
"no signal found" and goes back to sleep.

This is Mate on Debian Testing, but I recall it happening on earlier
versions of Debian as well using the DisplayPort and the XFCE desktop.

The exact same monitor wakes from sleep just fine when using dual-link DVI
with the previous computer it was on.  This is some sort of DisplayPort
problem between Debian and/or Gnome2-based desktop environments.  This
computer doesn't have DVI, just DisplayPort, or I'd just switch to DVI and
call it a day.

I can immediately get a command prompt, login and do whatever I want by
pressing <CTRL>+<ALT>+<F1>, and typing *startx* tries to load Mate, but
doesn't load properly ("could not acquire name on session bus"). The only
way to get back to the desktop I was using is to restart the machine.

Does anyone have any suggestions?

-Wes