Windows 7 64 bit
Nvidia GTX 750Ti
Broken: (2.75.4 946b850)
Short description of error
In Blender Internal material nodes:
If you use the UV output of the Input>Geometry inside a node group without using it outside, the UV coordinates won't be correct.
Exact steps for others to reproduce the error
In the node editor, you can see a node group ("TestTexture") connected to the material output. The node group contains a UV input, connected to a texture node.
The other two nodes are unused.
If you press render, you should see a textured cube, but you don't, because of the bug.
But if you re-render with the UV output connected to the input of the RGB to BW-node (or any other input), it will render correctly. Even though these two nodes aren't connected to the output at all.