iMac G5 als question

[padsf1]

Hi just bought an old iMac G5 20 and everything works great, 1 problem though. When the computer loads up on OSX leopard the screen goes dotty on the blacker parts of the wallpaper for a few seconds and then they disappear. Now that's on the highest resolution, once I take the resolution down a setting it doesn't do it? Anyone know what's going on? Thanks

 

[MagicBoy]

Most likely troublesome VRAM for the ATI graphics. Wasn't unknown with the R300 series GPUs