I've two odd graphic glitches in Sins which I think may be game related rather than my computer setup.
First off - all graphics set to highest, running res at 1680x1050 at 60hz (spec at end of post!)
1. I get dark banding around planets, this can be removed by reloading, but this may then occur on another planet insted - its quite difficult to pin exactly what causes it, it is on a particular zoom level as well.
2. The black space background is replaced when you reload to a default 'blue' background which will not vanish no matter how far you zoom out. This is easy to reproduce, start a new game, save it then reload.
Awesome game, looking forward to playing the campaign later! 
Spec -
Windows XP service pack 3, 2 Gig Ram, Nvidia Geforce 8800 GTS Driver 175.19, C-Media Sound Ship (latest driver!)