Strange...only my vertical cabinet experiences this issue...the horizontal one doesn't. Being that the vertical cabinet started out as a clone of the horizontal makes it even stranger.
During the intro animation sequence (not the game animations, but the movie file that plays before the front end loads...in my case I am running the shortened 80's arcade mpg), about 1/2 way through the animation it appears that MAMEWAH loses focus (as the taskbar "hidden line" appears)...and when this happens the animation sequence stutters for a bit then runs fine.
Any way to fix this?