applying Group policy Preferences "Regional Settings" In Vista can have unforeseen results

I am working on a Windows Vista migration project, where i am responsible for designing group policies for Windows Vista. After applying regional settings through Group Policy Preferences, the testmachines started showing strange behavior. These issue's started showing up after the first reboot, since the policy was applied.
These are the symptomes where noted:

1. Client where unable to get an IP address (no ip address could been leased/renewed), although the required services where running. The client did recieve an IP during PXE boot proces (comes from the same DHCP server).
2. The eventviewer was unavailable, allthough the services where running.
3. Unable to release/renew the IP address (RPC service unavailable). Remote Procedure Call service was running fine.
4. Somethimes the test users where unable to log on to the computer.

These isue's where not related to the user, because even after loging on with the local administrative account the same isue's occured. I reinstalled the NIC's on the client, removed all applied policies from the registry. Rebooted the system but still could not get an IP. Troubleshooting also showed that the client couldn't communicate with AD during the Windows Boot Proces, also only cashed domain credentials could log on.

At first i thought there was a problem with the image used for the deployement of the machines. But after redeploying the system I saw there was no issue as long no policies where applied. This pointed me towards the applied policies. The policies where devided in several smaller policies:

1. A general Computer policy (Common Computer policies Desktop Laptop).
2. Desktop Policy (Specific Desktop Policies)
3. A general User Policy (General user policies)
4. An Internet Explorer Policy (General Internet Explorer Policies)
5. An Office 2007 policy (General office Policies)

Started applying the GPO's one by one, which showed that the havoc started after applying the general user policy. This made the GPP's my number one suspect. Braking down and applying the policies over and over again proved my point. After applying the GPP's regional settings the isue starts to occur. Even when only applying the GPP's (no other policy applied) the isue's start to appear.

Compared two registry exports (one before and one after), in the hope to find what was causing the issue, but failed to find the registry entries which where causing these issue's. My troubleshooting did however show that the problem does occur after applying the GPP regional settings.

I did the same testing on Windows Seven RC1, and saw that these issue's are NOT occuring on Windows Seven.