Dave,
I'm sure you must have run across the ad without noticing it.
It appears near the top of your 'My Ebay' page, below the search box and above the 'My Ebay Summary' heading .
The Ads are changing all the time and can be related to any number of products that you have been looking at on the web.
At the moment I have a Barclaycard ad showing.
Yes, I have tried disconnecting the router, almost every time, but it doesnt help
when the Vodaphone ad is showing.
I'd be interested to know if you come across it during the day.
Thanks....N