Finding source of a problem flash ad

[masm50]

Hi all,

I am havinga bit of trouble with an ad on one of my sites. Somehow an ad has slipped through the filters at one of the networks I'm using.

Here's a capture of the ad (it's flash based so I can't show it properly)
http://img139.imageshack.us/img139/1006/badadyt9.gif

The problem is not the leaderboard, ut the site it spawns.
It pops up errorsafe.com to error check with various download prompts.

Is there some way I can check which network is serving a flash based ad?
Obviously if it is a gif/jpeg then I can right click and find where the ad is being served from, but how can I do this with Flash?

Thanks

Tim