I followed the steps at the link below to remove the proprietary driver and install the Radeon open source driver.
RadeonDriver - Community Ubuntu Documentation
However, now I notice that when I'm editing text (such as in this website) if I delete lines a few adjacent lines may completely disappear until I scroll or edit again. This bothers me enough that I need to make a change. Should I go back to the proprietary driver?
I'm running Kubuntu 12.04 with a Radeon HD 6750 card and 3 monitors (one at 2560x1600 resolution and the other 2 at 1920 x 1200). Maybe that is too much for the open source driver?