Fonts get bigger when 'past special' excel 2007 chart to P..

Hello,

I have an excel chart - (excel 2007).
I copy the chart and 'past special' it in Power Point 2007.
then I start the presentation (shift+F5 or click on the icon) and the fonts
of the excel chart became bigger and bold.

I saved the Power Point file (that now has the excel chart inside) as 2003.
checked on office 2003 pack and it works fine on Power Point 2003.
How can I fix it on Office 2007 pack?