While the account may be a domain administrator this may not matter especially if UAC is the root cause. I would recommend logging into the PRM server as the default local administrator account to access the admin portal to check the first step. If the local administrator account is disabled then explicitly give the logged in account local admin (even if it has it as part of a security group).
Thanks for the update again. I've tried that as well and still had the same permission error. As a last ditch effort and since the product hasn't yet been full configured I performed a full uninstall and reinstall. Success.
I am unsure as to why the error message began and wish I could have found the root cause and actually fixed it but I am happy to just have it running. I'll complete some testing to verify that everything works properly and if the issue appears again I will update. Thanks.