Wow, I've never seen this happen. Is this with PPT 2003?

You could ungroup the chart, which would remove the underlying data. Because
of that, I'd say ungroup a copy of the chart. Move the original off the edge
of the slide where it won't show during the presentation and right-click and
choose format to size it to, oh, 5% x 5%. That way it's really small and
won't make your slide jump to the left when you're scrolling through in
normal edit view....