If you are using ClarisImpact 1.0, and find that your chart legend is covering part of your chart information, try the following:
With your chart frame selected (there will be small, black, square selection handles on each corner) choose Legend & Title... from the Chart menu. In the Show Legend portion of the window that appears, make sure that both Overlay Hor. and Overlay Ver. are not checked. If they are both checked, the chart will stretch to be as wide and tall as possible in its window, and the legend may overlap part of the chart information.
This is also true for the Title.