We've been getting these since maybe 1.4 but it's been a lot worse since 1.5. The log just fills with about 40 of this event within the same second and causes major log and the user usually gets disconnected. We had MCCheat and this problem was still present. I decided to remove it and problem was still present. We had fly disabled until yesterday and it kept crashing the server when people used flymod. (well it's what we thought). So we enabled flying yesterday. But same problem happening today. I tried to google but it seems pretty vague and I dont see how to fix this. We're running on linux, that's about all we can get. We're using minecraft-servers.com hosting services.