Whenever I play nightlong, I get graphic corruption in the game using the ppc exe (big or small)the lines go away when I walk thru them or go to the next screen, but they just appear somewhere else. pic included

I only get this on the ppc exe, if i use the 1.1 or 1.2 68k exe the game runs fine without any corruption but it has alot of slow downs. so I'm wondering if any of you guys will have a clue on whats causing the corruption
setupA1200, mediator LT, Voodoo 3,PPC,all updates bb1/bb2/warp etc etc rtg master.