-SUMMARY-
I expected that the server would work fine,but then...
The server started lagging then it suddently crashed
Describe what happened here

Steps to Reproduce:
1. Open a 1.6.2 normal server
2. Make more than 2 players join in the same time
3.The server will start lagging,then
Any entity in the world will start overloading and
breaking the server.(Picture below)