Totally nothing to do with skins. I can see you are using one of Martin's skins. When I make skins, there is really no option where we can control how wide those screens (windows) has to be... that's code issue... I had almost same problem with wideness of my Settings windows in avast! I reported that problem to Alwil guys, they fixed it and in very next program update problem was gonne. Problem was fixed in about less than 5 days...
Cheers !