Do you see the same when casting a spell?
That the Flame Burst rather looks like plastic foam because it adds more and more content, and suddenly disappears, instead of getting slowly more transparent, as you would expect from a burning and out going flame?
That the sparkles from an arrow stay solid in the air, that you are afraid to walk against, instead of scattering and disappearing more and more after the arrow hit its target?
I can report this flaw for a GeForce2 GTS and an ATI Radeon 6250: It seems like the effect is frozen at the end of the time it takes impact on the target.