Windows Vista/7 32-bit Rocket-powered Punch creates visual effects in random places (in addition to in the flight-path)

The offending visual effect can be seen in the top-right corner, it's even visible in the fog-of-war.
The mist that is supposed to make up the flight-path of the projectile isn't visible here because of the timing of my screenshot, I think, just the end of the image sequence.

Not game-breaking or even game-altering, though.

 

Just wanted to confirm that I see the same error on both Win XP, 7, and OSX.