Due to other previous testing, I already have added the "Everyone" group to the GPO's security Delegation list. This would cover a literal idea of everyone, correct?
Also, so do you mean to say that a user on the local client computer is what needs to be able to access the .MSI,.MST,&.CAB? So instead of it being like DOMAIN\DomainUser trying to access the files apart of the GPO, it is something more like CLIENTCOMPUTER\LocalUser trying to access a networked shared location? If so, could it be that it is getting stuck essentially when you would be asked to provide a network user and password if you were to navigate to the shared location from CLIENTCOMPUTER\LocalUser??