Every time I open any MSN site I get the annoying pop up from ad.uk.doubleclick.net> demanding a username and password. I then have to cancel the popup before going on. Then it starts again with every new page. Have I inadvertently downloaded a nasty? I use Sybot S&D1.2 and Ad-Aware 6, both up to date, after every session, and they have not located a doubleclick.net> on the computer.