This is a lighting issue I have observed in 1.3.2, 1.4.2, and 1.4.4.

I'm in a large room at y=9, and the center cursor is pointing at a wall at z=450.

The attached set of 21 pictures show me walking in straight line towards this wall, moving from z=406.5 to z=426.5 by unit increments.

At z=406.5 (first pic) you cannot see the opposite wall.
At z=416.5 (2012-11-11_23.18.15.png) you can see it clearly.
And at 426.5 (last pic) you cannot see it anymore.

Because of this, moving in this room is very weird. There are some positions where you can see the entire room clearly (it's 50-block long), but when you move towards one of its extremities it progressively fades into the dark before becoming visible again...