I first posted of this issue under hardware but realized it must be a cinnamon-specifc issue, as I've also got Fedora 17 on the same machine, running Cinnamon 1.6.7 and it displays exactly the same - the desktop is about 20 pixels wider than the monitor, aligned properly from the left so that part of the far right of the display is missing; half the scroll bar of a maximised window is chopped off, as is the panel clock's last digit. I can provide screenshots if it will help explain.
I have another machine with Mint 13 and also Fedora 17, both with Cinnamon 1.6 and they both display normally through the same monitor. The screens/displays settings are the same on both machines: Goldstar 19" 1280x1024 . Is there somewhere else I can check?