   portablility issue
  So I made a couple very simple apps using DirectX 9. One is simply a wireframe cube. This works fine on all the computers on which I've tried it. The other is the same spinning cube inside a box. This works fine on my computer, but on another computer it seems like it has lost a vertex, and all the bottom corners of the outside box all end at one point, instead of there being a square floor. On yet another computer, all the triangles end up on the same plane. I am using the D3DX library to do my matrix transformations, etc., but for some reason, it seems to either lose a vertex or transform everything to one plane. Has anyone seen anything like this before and might know what the problem is? Thanks for the help.   
  Wacky behavior. I can't say for certain since I've never had this issue before, but absent some other more specific solutions, I would start by examining the differences between the two machines, specifically which version of DirectX is installed. I can't imagine why an older version would behave so differently, but it's a start. Also, check the code for any places where machine specific issues might arise. Good luck.   