A client's AdWords campaign experienced some unusual behavior over the weekend. Their account normally triggers tens of thousands of impressions and thousands of clicks a day. Then without warning Google stopped displaying the ads and the traffic dropped to zero or almost zero (let me explain). For 23 out of 24 hours the account would sit frozen, no new minimum bids, no paused ad groups, no disapproved ads – nothing changed accept there were no impressions or clicks. Then for 1 hour everyday it would resume it's normal activity. Strange and worrisome.
I poked around the forums and asked a lot of questions, but when you need information quickly and your problem is Google, the answer can be hard to find. So what did it all mean – well it meant that a Google rep was about to manually review the account.
In conclusion, IF your AdWords stops running your ads 23 out of 24 hours THEN expect a manual review of your account by a Google representative. If it happens on a weekend, you may see this pattern play out for a couple of days until your site gets to the front of the "review" line. AND best of luck with the outcome.