DPMS stops working (ATI, openGl issue?)

[Erik Steffl <steffl@bigfoot.com>]

  When I start X DPMS is working (monitor is turned off), however after 
some time it stops working (i.e. monitor is always on).

  When I run e.g. xset dpms 60 65 70 it works again (for some time).

  Only idea I have is that openGL unsets/reset/break dpms (that's about 
the only graphics weirdness I can think of that happens sort of regularly)

  Any ideas how to troubleshoot/fix this?

  system:

  ATI Technologies Inc Radeon R350 [Radeon 9800 Pro]
  Apple Cinema connected via DVI
  kernel 2.6.18
  fglrx-driver 8.31.5-1 (proprietary driver)

  Debian bugs don't mention anything relevant, net search revealed 
similar (same) problems but no solutions.

  TIA,

	erik