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) ?
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.