I'm trying to do very simple rendering.
My vertex buffer has 8 floats per vertex (3 for position, 3 for normal, 2 for texture)
I'm drawing two triangles, each having its 3 vertices, but I'm getting one triangle drawing ok, and the other with strange results.

These are the vertices (CCW, as required)

and the indices are simply 0,1,2 and 3,4,5

My texture is the test pattern:

and the resulting rendering looks like:

I would appreciate any idea on why this happens.