I moved my map from lots of sprites to just 1 vertex array and I was messing around with the window view making it follow the mouse(as in the future I will make it follow he player) and I get transparent lines at some positions.
this is the code:
SFML.Graphics.View view = new SFML.Graphics.View(new SFML.Window.Vector2f(wid/2.0f,80)
, new SFML.Window.Vector2f(wid,160));
window.SetView(view);
And this is what happens:
It seems to be picking up a line of pixels from the tile bellow it on the tilesheet