GPO affecting WinXP performance

I recently started implemnting a new GPO with our XP SP2 machines. After I started the policies the machines have slowed down by a lot, ~50% maybe.

It takes 3 - 5 mins for Outlook to even open.

Any idea what could be causeing this? If I turn off the policy the machine speeds back up to normal. I've gone through and can't see anything that should merit this sort of slowdown.

Anyone know what could be causing this?

Perhaps you could describe the settings of the GPO....

Mostly it's basic lock down stuff, limit access to regedit, cmd, remove last logon. The only thing I can think of that maybe causing it is my SUS settings, but I don't see why that should be causing this. It's only set to update at 3am.

With SUS the downloads happen at a (mostly) random time. 3AM is just the installation time. However, the GPO settings for SUS are only ready once by the Automatic Updates service when the service starts. To change SUS settings, you need to not only change the GPO, but also restart the computers affected by it, or at minimum restart the Automatic Updates service on those computers.

I don't know if that's the problem, but it's worth considering.