I get black borders when I am playing some games, I get it in Prototype for all resolutions and some resolutions in BC2. I never get black borders when I was using Nvidia cards. I tried underscanning, overscanning, and changing resolutions. I only get it if I am using HDMI, but when I use DVI, I never get black borders.
I have ATI Radeon HD 5770, my monitor is LG Flatron W2361V.