Hi,

Your network could be under DOS attack. This would mean that one of the computers (rogue computer) on the network is sending excessive SYN packets to every port on the server with fake IP addresses. Since the IP addresses are fake the server cannot close the connections thereby causing SYN Flooding.

This link could be helpful to protect your network against SYN flooding -

http://msdn.microsoft.com/en-us/library/aa302363.aspx

Thanks

Anand