[C0nw0nk]

Did a bit of research it could be a number of things due to configurations with your host at network adapters causing packet loss another thing it could be is Windows Packet Scheduler, It has hard to figure out with the little information you have provided what windows server version are you running ?

Another thing that could help determine the cause is perhaps a addon / plugin you have installed could be a error or conflict.

Also one of the first things i did state is if you are under any form of DDoS (Distributed denial of service) what is a completely different attack to a DoS (Denial of service). You should contact your hosting provider because it is really an attack that should be handled before it even reaches the server and be blocked at a network level by the routers.

//UPDATED : I updated the original post explaining the difference between DDoS and DoS adding in a F.A.Q area. To answer allot of questions about the massive difference between a distributed attack and denial of service attack.