Power Management Hangs/Freezes

I have a problem with Vista Home Premium in regards to Power Management.
Vista freezes/hangs if I select a power management scheme radio button and I
then need to make a cold boot to restart the system.

The system is also not going on standby or using any of the settings in the
active Power Management scheme, not that I can select another.

I have an Acer Aspire E560 desktop.

Any ideas?

It gets even worse. PC also freezes if I try and create a new power
management theme.