Gallery feature and Tannistha

Hi,
I´m trying to use the ordinary Gallery feature in WordPress (no plugin) together with Tannistha theme, but I cannot get the columns right. I want my thumbnails in three columns and it looks alright in the backend, but the frontend only displays one column. I have cleared the cache and deactiveted my plugins, but it didn´t help.
I tried to change my theme and then it worked alright, but I like Tannistha so I hope somebody would like to help me?

The page I need help with: [log in to see the link]