Ahh please be more explanatory than just throwing the error to us expecting us to do wizard work to find when and what for this error is called. As @teej107 usually asks, What have you Tried so far? What causes the error? Is it caused by a plugin you made?
@mine-care i have no clue whats causing the error, the error was thrown with 120 people on. yes we use WorldEdit and the rest are custom plugins
@ResultStatic mabe you need to focus your attention to Bukkit Help. This is a error caused when there is a problem with the handling of a packet. In this case I think it is due to packet play in position look, essentially an incoming packet telling the server about where a player is Stering at. It might be because you are using spigot and I assume it is the protocol "hacked" version letting 1.7.X and 1.8.X clients in. The issue with these builds is exactly that they need to handle each packet differently because packets come from different clients with different structures ect. So a mishandle can easily occur. Hope that helps at least a bit :- )
@mine-care hmm that could be it, we dont allow 1.8 in for a few seconds anyway because some of our code doesnt support it, i could just block any movement packets from 1.8
@ResultStatic wouldnt say so. Keep in mind that everything has its disadvantages and advantages and we try to find whitch of those fits the best for us So in your case yes it might be but for me, i like Bukkit =D (thats why i am on bukkit forums)