drall - 9:23 pm on Nov 2, 2008 (gmt 0)

According to the Google Adsense Program Policies page yes but you have to make sure the AdCenter ads cannot be confused with Adsense ads and as Googles Program Policies page says this is your duty.

"Competitive Ads and Services
In order to prevent user confusion, we do not permit Google ads or search boxes to be published on websites that also contain other ads or services formatted to use the same layout and colors as the Google ads or search boxes on that site. Although you may sell ads directly on your site, it is your responsibility to ensure these ads cannot be confused with Google ads."

We usually run different fonts/colors/formats to make doubly sure there can be no confusing the two.