Power Mac 6500 and video out problem

An anonymous source who works with numerous different monitors (AppleVision 1710's, Multiple Scan 15AV's, avariety of 17" Viewsonic's) reports the following problem with every monitor he connected to a 6500: Especially at higher resolutions (1024 x 768 and above, although it's noticeable even at lower resolutions), a shimmying, wavy distortion pattern appears in the display, most noticeable along vertical edges like on menu rectangles. Apple Tech Support acknowledged the problem and implied that there will be a software fix.