GUI buttons look fine on full screen but distorted otherwise?

I have created a .tiff file from photoshop that includes an alpha channel for rounding the edges. I added this to my GUIskin for button normal, but when it renders it looks like some of the texture stretches to either side of the button beyond where it should. This is not a problem if I maximize the screen or if I build the game, but when I build the game the screen is big also. I did not use "alpha from gray scale" either. Any thought as to why this would be??