You experience a long domain logon time in Windows Server 2008 R2 after you deploy Group Policy preferences.

Article ID: 2561285 - Last Review: August 10, 2011 - Revision: 1.0
You experience a long domain logon time in Windows 7 or in Windows Server 2008 R2 after you deploy Group Policy preferences to the computer

Assume that you have a client computer that is running Windows 7 or Windows Server 2008 R2 in a domain environment. You deploy Group Policy preferences (GPP) to the client computer by using item-level targeting using security groups. In this situation, a user of the client computer experiences a long domain logon time. This issue becomes more noticeable if the domain controller is only reachable over a slow link.

This issue occurs because item-level targeting uses recursive group membership queries to determine which groups the computer is a member of. The expected behavior of item-level targeting is to query the groups that the computer is a member of.

Source: http://support.microsoft.com/kb/2561285/en-us?sd=rss&spid=14134