[SOLVED] Help: error instead of UAC prompt??

All the computers in our office are set up with an Administrator account that's no longer used, and with a new Standard account. As I've been setting up the Standard accounts, I naturally get a UAC prompt whenever I take actions that require Admin privileges. It works exactly like it sounds, and looks like this:


But here's the problem: on one of the computers, instead of getting that prompt, I just get warnings indicating that the task isn't allowed except by administrators. How do I make it so I get the prompt for tasks requiring admin privileges instead of a warning/error indicating that only administrators can carry out the task?