Killing a demon ...

• OpenSUSE 11.4
• Ubuntu 11.04
• Various ATI™ graphics chipsets

Symptoms:

• The screen will go black about every 30 seconds (flicker).
• The system 'freezes' about every 30 seconds for a few seconds (mouse, keyboard actions does not have any effect).

Probable cause: There might be a problem with upowerd polling information in conjunction with linux ati drivers.

Solution

There may be better ways to solve this problem, but to me the disturbance caused by upowerd appears to be very annoying.
So, I decided to remove upowerd from the system. At least on desktop systems this seems to be a minor disadvantage.

Usually, the demon is located at '/usr/lib/upower/upowerd'. Simply rename it to something like 'upowerd.old', restart your system. The problem should be solved by now.

Maybe, in future there will be a better version either of upowerd or the graphics driver.