Cannot drag widgets to desired area

Dear all,
I’m using the Advantage theme for my website. In the ‘widget’ section of the theme, (in the administrator’s dashboard) I should be able to drag and drop widgets to the widget areas listed on the right side of the screen. However, I cannot seem to pick them up and drag them to the desired area; they just won’t move and aren’t clickable in any other way. Does anyone recognize this problem/know a solution?
Many thanks!
Sophie