Just piping in with another "confirmed problem" report. I get the wireframe skybox problem in JAD, but no giant circles or anything. Nvidia 960GTX, 347.25 drivers. It only seems to be occurring on certain types of skyboxes that have more than one sub-object. It happens in FRED too.
(Also jump nodes don't appear to be rendering in FRED)
Skybox issue problem mantised: http://scp.indiegames.us/mantis/view.php?id=3161