When a user logs on to a domain from a Windows Vista-based client computer, the client computer takes a long time (about 10 minutes) to process the logon script
Consider the following scenario. In an Active Directory domain environment, you deploy a user logon script to client computers in the domain. The logon script contains calls to Active Directory Service Interfaces (ADSI), such as Lightweight Directory Access Protocol (LDAP) queries. However, every time that a user logs on to the domain from a Windows Vista-based client computer, the client computer takes a long time (about 10 minutes) to process the logon script. During this time, no other ADSI queries can be executed.
This issue occurs if the ADSI call in the logon script involves downloading a schema cache file.
For more information on this issue, including potential causes, workarounds, and resolutions, see: Microsoft KB Article KB952611.