You can push out registry keys or values using GP Preferences (GPPs):

Comparison results table : http://timstechnoblog.blogspot.fr/2010/10/group-policy-preferences-registry-items.html

If you are deploying multiple keys through GPPs, things to look out for are Order of GPP and the path of Key.

For e.g. You may be overwriting a key location which you created at order1 by using the Replace action on the key at Order2 because it falls in the same path.

For GPPs and deploying Registry Items:

All User Configuration Registry Keys fall under HKEY_CURRENT_USER (Deployed Under User Configuration–> Preferences)

All Computer Configuration Registry Keys fall under HKEY_LOCAL_MACHINE(Deployed Under Computer Configuration–> Preferences)

GP Preference (create,replace,update,delete) ?

http://www.windowsecurity.com/articles-tutorials/windows_os_security/Group-Policy-related-changes-Windows-Server-2008-Part4.html

http://blogs.msdn.com/b/microsoft_press/archive/2009/09/29/william-stanek-applying-group-policy-preferences-with-crud.aspx

http://www.blackforce.co.uk/2013/01/27/create-delete-modify-registry-keys-using-group-policy-preferences

Troubleshooting:

Also, will help to have a GPResult /r Run from a Command Prompt (As an administrator to include computer policy results)

You may run a GpResult /h “FILENAME.HTML” which will give an easier read of what’s applying/what’s not.

This must be run from the client computer, logged in as user if possible.

Tip: RSOP.msc can also be used (more user friendly)

If you are looking for General Group Policy Troubleshooting Guidance, you can find some good info here.