site title displays twice

so on my wordpress site (proboxinginsider.com), i installed an SEO plugin called wordpress seo by yoast. i like it except that it makes the title of the site appear twice. i dont get it. its happened to many people since i find info about it while searching. however, i cant find anyone talking about it in a language i can understand. i am computer stupid and need my hand held, not a bunch of language that confuses me.

so if there is anyone out there that can help me, i would appreciate it. just please explain what you mean before you get all technical. thanks