[commodorejohn]

The issue with the O2 is that, despite using a VGA output, it still includes the sync signal in with the green signal like on older *nix workstations. It's more compatible with modern monitors than those because it does provide the separate sync information on the dedicated VGA sync lines, but for monitors that aren't designed to cope with this, it will still count as an overall boost to the green signal and you'll get this. You'll want to find a monitor that can handle this; I use a Samsung Syncmaster 173p and that handles it just fine.