While doing some maintenance and upgrading a backup server I noticed that the mysql dumps that are done before rsyncing daily were too small. We had just a production database over to this server a few weeks ago, and I was assuming that the dumps were happening since I wasn't getting an error in the logs.
This was on a machine we inherited from another IT provider, and it turns out that the mysql database had been languishing for a while and wasn't updated after a mysql upgrade some time in the past. After finding some googling I found another blog post describing the same issue. Nice quick little fix for what could be a sticky problem.