Well, if the problem is indeed in pg_statistic, it'll be easy to repair (think TRUNCATE...). Have you turned up the logging level to find out?
BTW, please don't do anything to try to correct the problem until we're pretty sure we understand how this happened --- we might ask you for more info. AFAICS this isn't having any bad effects except for bleats in your log file, so you can wait.
We turned up the logging this morning.....(debug2) and are awaiting the issue to re-occur. Will report back then. Thanks.
