blank screen when adding item image in K2 component

Hi,
I just installed Sporter template and I saw that I have a problem when trying to replace an image item in k2 component.
Simply, I choose the new image, I click the Apply button and after this I see a white screen in administrator page. Most important, the new image has not been saved.
Obviously, in this way I can't modify the content as I wish.
Please help me with this.