Short post today but another good two posts from the Directory Services team on how to enable Userenv logging for troubleshooting Group Policy. This comes in handy if you do not do this all the time.

http://blogs.technet.com/askds/archive/2008/11/11/understanding-how-to-read-a-userenv-log-part-1.aspx

http://blogs.technet.com/askds/archive/2008/11/11/understanding-how-to-read-a-userenv-log-part-2.aspx

Some useful links on Group Policy Troubleshooting on the client side.

Enabling Debug Logging on the Client Side

http://support.microsoft.com/kb/221833

Troubleshooting GP Client Behavior

http://support.microsoft.com/kb/216358/

Troubleshooting GP Applications (More General GP Client Side Troubleshooting)

http://support.microsoft.com/kb/250842