"The content you wanted to modify was to big or small to fit on the Prezi canvas"

I have an issue with my Prezi (http://prezi.com/h05aywfr4q8f/sverige...). If I try to modify anything I get an error message saying "The content you wanted to modify was to big or small to fit on the Prezi canvas".

I think I have accidentally enlarged a frame so it became a horisontal line running through the entire canvas. I can't find a way to erase it. Any help would be much appreciated.