Screensaver and power management stops working

[Marcelo Magno T. Sales]

Hello,

In a desktop machine running Kubuntu 9.04, every now and then the 
screensaver stops working (does not initiate) and the monitor stops 
being turned off.
If I logoff and login, everything works again. It seems to be a KDE 
problem, not a Kubuntu problem, because I've seen this behavior before 
with other distros.
However, is there a way to make it work again without having to logoff 
and login?

Thanks,

Marcelo