Logo positioning?

I change the logo on my forum regularly and its always showed up fine on the forum but this time the logo has covered part of the navbar as well. I've already resized it a couple of times and it hasn't made a difference. I don't know whats wrong with it because I've had logos bigger than this one before and they haven't covered the navbar. How do I get it to fit?

http://www.theguineapighutch.com/