Why does my display turn back on immediately after turning off?

[Celejar <celejar@gmail.com>]

Hi,

On a recent Debian install with XFCE, display power management was
initially working fine - the display would blank and turn off after a
certain amount of inactivity (apparently handled by XFCE's Power
Manager). I subsequently played around with some things (installed
Xscreensaver, played with its settings and those of XFCE Power
Manager), and some time elapsed, and now this functionality is broken -
now the display turns off, but it invariably just turns back on
immediately.

I have removed both Power Manager and Xscreensaver from the system, and
the problem remains with just basic DPMS: I issue 'xset dpms force
off', the monitor turns off, and then turns right back on. 'xset q'
shows that DPMS 'Standby', 'Suspend', and 'Off' are all set to '60' (I
initially set them via Xscreensaver, while still installed) and DPMS is
'Enabled'. With these settings, the monitor turns off once a minute -
and then immediately turns back on. What could be doing this?

I'm pretty sure it's not a question of mouse sensitivity - it happens
even when I'm away from the computer, and nothing is moving in my
setup. I even checked with 'xinput --test <mouse_id>', which shows no
mouse movements.

I can't think of any other software I installed that may be interfering
with display management, but I could be missing / forgetting something.

Any ideas?

Celejar