Windows Vista Windows security center

I am running Vista Home Premium system, 64 Bit.
When I go to windows security center, it is turned off. I cannot turn it on.
When I click the turn on now button, it says windows security center cannot be started.
on the menu on the left, when I look at windows update, that is running normally and files were automatically updated today.
My firewall on the left hand menu says it is on also.
but on the right main menu I cannot turn the security center on.
What is the problem?
I hope this is not the conficker worm.
can anyone help?
thanks
Barbara