Weird chart window size problem in XL07

Recently upgraded from XL03 to XL07. I use excel to create a chart that I
then publish on the web.

Upconverted a workbook, and something odd seems to be happening on the chart
page. When I open the 07 version of the workbook, the chart itself seems to
be the same size, but the window for it is much skinnier. Chart area is about
1/5 of the width of the screen (rest is greyed out), and the actual chart
extends a long way underneath the grey.

If I go to page layout -- size -- ledger, the window goes back to normal
and I can see the entire chart at one time. But if I save as web page, the
web pages revert to only showing a small portion of the chart.