Screen Flicker Problem

When I go to full screen when playing Opaline, the game screen flickers rapidly and I have to revert to windowed mode. Unfortunately, that window is way too small to play the game. The same situation occurs with Ashes of Immortality. Moonchild, however, plays just fine.
Has anyone else had this problem? If so, were you able to resolve it?
And before anyone wastes their time suggesting it, all my drivers are up to date. I'm running Windows XP, SP3 with a Radeon HD 4670 video card, 2GB RAM, and a 1080P Full HD Viewsonic monitor with a native resolution of 1920x1080.
Has anyone else had this problem? If so, were you able to resolve it?
And before anyone wastes their time suggesting it, all my drivers are up to date. I'm running Windows XP, SP3 with a Radeon HD 4670 video card, 2GB RAM, and a 1080P Full HD Viewsonic monitor with a native resolution of 1920x1080.