Group Policy issue

Recently, my organization has been implementing new security policies. Due to the new requirements, I have enabled the screensaver lock after 15 minutes of inactivity and have specified a fully qualified path to the screensaver I wish to be applied. The problem is the policy only works on about half of my workstations.

All of my client computers are Win 2000 and Win XP however, the problem is not specific to one OS. Some 2000 and some XP clients work and some don’t.

Any idea’s what the problem could be?