netmeg - 12:28 pm on Jul 8, 2013 (gmt 0)
Yea that happens, although if NONE of them are loading, I'd be more suspecting a network outage somewhere.
Google can't manually keep track of every ad, and sometimes advertisers do dumb things. I periodically get some 300x250 rich media on my sites that's just *blank* - can't even get a link off it - and I've complained repeatedly to AdSense but they say there's nothing THEY can do to detect it.
One time one of my clients' competitors took their entire site down "for maintenance" for a week (I suspect it was actually hacked) and forgot to turn off their ads. So all week they paid to send people to their "Down for Maintenance" page.
It's an imperfect system.