Group Policy Preference not applied automatically

DC - Windows Server 2008 R2

Client OS - Window XP

I have applied USB block Group Policy Preference setting for Window XP ( i.e Registry setting & usbstor.inf, usbstor.pnf denied policy ).

But one of the domain computer this policy was not applied. I don't know why.

Because of that we received shouting from the management while cross- checking.

When i check that PC and manually update the group policy with gpupdate /force command, than that policy get applied. How should we avoid this type of loopholes. Please suggest.

As well as let me know why not after 90 minutes interval this policy had applied.

How should i check when the group policy update has automatically applied, what is the event id for that?

As per my personal Experience

Mr Chris S is rights, to ensure that GPP is applied successfully you have to cross check with the Window XP Client. Remotely you can check the registry setting of all window xp computer to confirm your GPP