[Plugin: Promotion Slider] smaller images

Hi there.
I’m trying to setup Promotion Slider, but for some reason images are displaying smaller than they supposed to, and a blank band is appearing in the right side of the slider.
I’m using this shortcode: [promoslider width=”678px” height=”300px”]
And also setup WordPress to scale images to that same size.
You can see it in action here: http://www.paganopropiedades.com.ar/pagano/
Any help will be welcome.
Thanks in advance!

http://wordpress.org/extend/plugins/promotion-slider/