I have always managed to run Wolfenstein: Enemy Territory on my computer fine, with no flickers. And Enemy Territory still works fine; no flickers.
However, I recently installed PlaneShift, but this flickers like mad when running. It is completely unusable, because it hurts my eyes, and I can only see half of the screen at a time. It flickers fairly fast, about 4-6 times per second.
Does anyone know how to fix this?