Bump map node giving mesh blocky shadows and no lighting It's been happening the last couple of days, but whenever I attach the Bump node to diffuse or any other property, the mesh becomes darker and it gains dark blocky shadows, it almost looks like I've applied the toon shader on it. No matter how my times I use the subsurface tool, the shadows never smooth out and I never get my bump map effect. 
This is the exact beginning setup that I've done on multiple occasions, but recently it's been wigging out on me, I want to know the reason why it's doing this. 

Edit  The Second image is me doing the same beginning node setup with the outcome looking way different. There's something I'm missing but I don't know what
As cegaton said, connect your Image texture node to Height socket instead of Normal.
Also change the first dropdown from Color to Non-color data.