Hello!
it sounds like the clipping bounds are not right for the chart layer, but i'm not sure how to reproduce this problem. could you provide an image or sample code? there is an "options" tab visible when composing a message here, you can use that to upload an image of your chart or a sample project.
What I found out is that this only happens with StepLineCharts. I attached an image with 4 parts where you can see the different behaviour. Pic 1 and 2 show how an Line chart get cut off and Pic 3 and 4 show a StepLineChart that does not get cut off. Here a line is shown right at the boundary. (The left pics are with auto axis and the right pics are with intentionally to small axes.) To me this looks like a bug?
(By the way my IE (7) crashs all the time when I try to upload a file.)
Uli