The video drivers for OpenGL in Windows just generally tend to be a lot more problematic than Direct3D drivers. That's actually the main reason why I went with Direct3D for MoI in the first place.

Rhino has become more and more unfriendly to low end systems as time has gone on, there are several video cards that their support staff just flat out says not to use with Rhino: http://wiki.mcneel.com/rhino/videocards

Direct3D drivers can sometimes have bugs in them as well, but because almost all games use Direct3D, those drivers just get a lot more testing and improvement effort put into them so usually the number of driver bugs is way way less with Direct3D.

Then there's also the problem that video card manufacturers seem to intentionally degrade their drivers for their "low end" cards and try to require people doing CAD work with OpenGL to purchase the $1000+ "workstation" type cards instead.

- Michael