Screen tearing help

I recently switched from a gt520 to a hd5670 that I got for free. I will he using this card for a few months until I can get a hd7770 or similar. With both of these cards I have experienced a small amount of screen tearing only when moving quickly in a game. What could be causing this?

Other specs:
Phenom 2 x4 965 black edition
8gb ddr3
160gb HDD 1.5gbps
Gigabyte 78lmt-sp2 revision 5.0
Acer 23in monitor 1080p VGA connection