I'm no longer seeing the ads, since I changed browsers, and somehow found a way to opt out. Now I am getting this message in the ad banner:

This ad has been matched to your interests. It was selected for you based on your browsing activity.

DoubleClick helped American Express determine that you might be interested in an ad like this.

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I found it interesting that the ONLY ads which prevented the forum pages from loading beyond the top ad banner were American Express ads. All the other ads worked fine, but were difficult to rotate through, especially on a forum like Delta, where AmEx ads seemed to predominate.

Thanks for your help!