We have implemented a machine based group policy for our domain. We use this because we have different locations that have different proxy settings (same domain). The policy went into effect and was successful on 90% of our client pc's. The other 10% we are having to do a gpupdate /force and it usually has to be a local administrator of the machine to do it. There is no rhyme or reason to it.
The computer policy is under Computer configuration / preferences / Windows Settings / Registry.
There are three keys ProxyEnable, ProxyOverride and ProxyServer.
As I said it worked fine on 90% of the machines. Any help would be appreciated.