Commonly, skins are made for 16:9 aspect ratio, you are probably using one of those skins.
I believe 1440x900 is 16:10, which would explains why it's "obstructing" some of the elements, not sure if this will work, but try using "Letterboxing" to make your osu! in 16:9 aspect ratio, this would result some black bar around the screen though, or you could modify the elememts to 16:10 by using some programs (not sure if there's an automatic one, probably you'll have to the image manually using Photoshop or some kind).
Or you could just find skins that support 16:10 aspect ratio.