What OS are the clients running?
To have an immediate update for XP, type the following command and reboot your machine:
gpupdate /force
(Incidentally, have you run RSOP.msc to see if the updates are applying?)
To have an immediate update for w2k, type the following commands and reboot your machine:
secedit /refreshpolicy machine_policy /enforce
secedit /refreshpolicy user_policy /enforce
To force your GPO's to update on a more regular basis, go to your Group Policy editor, and the following location and check out some additional settings you can deploy:
Computer configuration->Administrative Templates->System->Group Policy. There is an option to control when and how often the policy is applied....