screensaver and power saving stopped working

Imac 27"

After the latest update (april 16th 2011) my screensaver doesn't start and the screen blanking in power settings doesn't work either.

Until the update the screen saver started after 5 min and the display switched off after 10 min, but after I applied the latest update none of these settings works.

I have tried to "reset to defaults" and the reapply the settings, but without any effect

The screensaver works if "test" is pressed, but not if the timer has to start it.

Have any one seen the same problem ?

Carsten