About 20 hours. We had a major campaign for a product launch back in the days when MSN Messenger was awesome. Hitting F5 in MS sql query analyzer to execute query again would show like 20K+ downloads each time, shit was crazy. Then we discovered a major fuck up. Turned out that someone made a mistake by making a guid static. In a personalized content generator. So, most users ended up with someone else's face inside their personalized MSN Messenger wink. Oops... and no, we didn't do code reviews nor TDD back then so we didn't discover it sooner. It was really awesome to see how much traffic MS could generate by just showing a banner in hotmail. Real crazy. Anyway, we fixed it, discovery of the actual problem did take some time though.