ALL of the ads? EVERY SINGLE AD? If that's the case, then that site might be banned, or maybe your entire account.. is the site new, or did you just put the ad-code on? can the Adsense-bot access your pages? what's the URL ?
its the bookmarking site in my sig. i mean its not all the time. sometimes it back to normal. Google did e-mail today to verify my number and address. they said they are gong to send out a postcard with a pin number.