Hi nhykoro
This may be an ACL (Access Control List) permissions issue, do you receive any error code associated with this in Event Viewer? Read
This page to see if this may be what you need to fix this.
It could also mean that your WinUpdate client is corrupt and needs to be replaced. That can be done thru MS email support for free. I had the instructs around once and the needed commands but I think I neglected to save them.