Hello Carl,
I've just figured out what was happening. Very confusing, but i had the date changed on my system to a date in the future as I had date sensitive info inside the ad. As soon as i changed the system date back to "set date automaticaly" everything is now working again - i'm on a mac by the way. And of course the client was having the same problem as they would also be testing the date functionality out.
It isn't just my ads or the ads you posted by the way. If you change the date on yoru computer to a custom date half the sites on the internet on firefox don't seem to be working! Interested to see if you get the same problem....