Portfolie images get different sizes

I downloaded the demo content to my site, but portfolio images are acting up funny. On your demo site the images gets one standard size, but on my site they get all sort of different sizes. Please can you help me understand how how set it to force one standardised size / cropping of portfolio images.

See examples:
http://preview.hb-themes.com/?theme=Highend compared to my site http://69.195.124.212/~sunnlede/portfolio-standard-3-columns/

and another example is on the front page http://preview.hb-themes.com/?theme=Highend compared to my site http://69.195.124.212/~sunnlede/

I really appreciate any help!