Windows Vista Group Policy Client Failure

The reason included the link is because your answer lays hidden in your system event logs (hopefully, I say hopefully as sometimes the answers are a little obscure). You can find these by going to you control panel, System and maintenance, Performance information and Tools, (in the left hand green column) click Advanced Tools and then at the top of the page Event log.. Trouble is, at times this can be like looking for a needle in a haystack..
You could also try this..click on the vista button (start button) and in the search box type 'services.msc' (without the quotes) and hit enter. You will now be looking at a list of services which operate on your pc, scroll down and make sure that Group policy clent is set to 'automatic', if it isn't change it..