I get this particular problem with eBay and not any other advertiser. I have been told its something to do with the wordpress CSS, but I not knowledgable enough to follow through.
See the eBay advert part way down in the post one of my sites:
see how it is all broken? - it should be a neat 468x6o banner
It does not occur in the default WP theme, so is an issue with the theme. HOWEVER, I do have the exact same problem on two other WP sites, all with different themes from different developers, so posting here rather than initialy following up with theme developers.
The eBay adverts (like all my adverts) are being served up via Openx, but the problem still happens when I directly insert the ebay code to bypass OpenX.
I did ask at the OpenX help forum when I first thought it could be related to OpenX and got this: "It looks like you might be having problems with your Websites CSS styles. It looks like there is a table border applied for your banner, that is why it looks a bit garbled."
I just do not know what to do about it. Any help much appreciated.