Ok, so, I added a handful of people to the local Print Operators group (via an AD group) on a file/print server. I also manually added Print Operators AND the ad group to the security ACL for the individual printers (after noticing that Print Operators wasn't in the ACL by default). I did the same thing to the print server itself via Print Management\Print Servers\server.
However, the users who (and I've verified this several times) are in the AD group still get the above error when RDP'd into the server, when they go to Devices and Printers, find the printer to manage, bring up the print queue, and select Open As Administrator. Specifically, the error is referring to c:\windows\system32\printui.exe.
Also, UAC is at the lowest setting, which I know doesn't actually mean disabled in Server 2012, but I figured I would mention that as well.
Any idea? We trust these people, but not enough to give them local admin on the servers, so that's not really an option at this point. And they're not all local to the sites they support, so while managing them remotely by installing the printers onto their systems is an option, it's not a fantastic option (opening the print queues would be a bit slow).
Best Answer
OK, I figured this out yesterday but forgot to mark the answer.
Basically, I lied earlier (not on purpose) about the domain Print Administrators group being given full control of the printers. I added it to the ACL of the printers yesterday, and one of the on-site admins verified she was then able to manage print queues. So, it appears as if the local Print Operators group being added to the ACL (with the domain Print Administrators group being a member of that) didn't do jack.
So again, I'm guessing this is due to a UAC oddity with Server 2012/2012 R2, but at least it's resolved now.