bug with every quad face (just create plane):
enable 'draw faces' in mesh tools 1,
hide (and reveal) consequently every vertex
(one at time!) of quad face,
we expect that every time we'll have just three
vertex (connected by two edges),
but in one case (not random) we see that the face
remain drawed.
If shading mode is solid we also get 'half face'
(triangle) on top of transluced.

I have suspicion that this is OpenGL bug
(or my video card: GeForce2 MX400 driver 6.14.10.5216
on WinXP)