Well, the guys at BannerConnect seem rather eager to help (they contacted me), so I've put one of them back.  Please tell me if you have any issues.
This is what they said:

Quote:The ads you are talking about are a problem. Thanks for informing us about it.
These ads are not served by BannerConnect, in fact they are in violation with our TOS.
However, wee get the ad tags out of the rightmedia system and unfortunately there are people who manage to disabuse/hack these tags.

Problem is, they are not in our banner rotation, so I can’t track them down very easy.
If you could provide us with more info or a referrer url this would help.
You can get this referrer url by clicking on the ad and hitting the escape button at the same time. A referrer url looks like:

http://ad.bannerconnect.net/click,AAAAAH...CAAECgIACg MkdAkAMfkIAHkuBwAAAAAAAA......

it is possible that you have to try several times before you obtain the url.

Thanks again and sorry for any disturbances.