Yes, as far as I know, often that coming from some render camera settings. There is also a plugin to remove that if you can't get rid of it in other ways. http://www.smustard.com/script/FixAspectRatio

@valerostudio said: ++1 on Vali script. You can use scripts in Free SketchUp, can't you? Well worth the price of $26 I have to tell you. Think about it, if its takes you 3 hours of your billable time to figure this out, isn't it worth it? This plugin has saved me hours upon hours of fence and railing modeling and I have only owned it for a couple of months. I was going to say. Not sure if there's a style for what you want, but if there is-- at those prices it's a question do they want to buy the SW or have you spend more hours? In the right instance VA tools eliminate a lot of tedious time drawing.

Thanks Cotty I tried that, seems to work ok.