On deeper digging regarding Distro Hunt it seems my graphics card may be the source of the trouble. Even though it's not too slow, my Nvidia 7900GS card was actually made in 2007 - 7 years ago, and is really legacy and being pensioned off by Nvidia.
Ben is always updating his system, and a quick enquiry regarding alternative cards produce a monstrous red ATI 4890*. Which in turn required 2 (!) power connectors, which required another power supply, which required gutting and rebuilding the inside of my PC after PCC meeting was over. So here I am at 11.45pm, having just finished playing Lego with computers in hardware (there's plenty of lego software already) just lining up a Sabayon install.
I *think* all my data is backed up.
*When it first started there was a loud 'whoosh' as the fans came on, then it all went impressively quiet. Excellent thought I, it won't have any load and will run nice & quietly. However as the KDE desktop came up, so did the fan speed, and it's far from quiet. I've a feeling a budget passive card is going to be on it's way soon - who needs to game?