The following problem has been experienced under Windows 7 and Windows Server 2008. It has been experienced on both NOD32 v4.x and ESET Endpoint Antivirus 5.0.2126.0. The ESET Protocol Filtering has a race condition which causes systems running NOD32 v4.x to COMPLETELY freeze (keyboard, mouse, video -- everything is froze) and ESET EA 5.x the specific processes hang in such a way that you cannot kill them or even properly shutdown the computer. The only way to keep my system from locking up is to uncheck "Integrate into system" on the "Protocol filtering" tab of the "Advanced setup" and then rebooting. The following Python script reproduces the problem within seconds of running it: Code: import socket import threading ip = '127.0.0.1' def server(): s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) s.bind((ip, 50020)) s.listen(1) while True: conn, addr = s.accept() conn.send('1234') data = conn.recv(20) if data != '1234': print "Server: Received invalid data" conn.close() def client(): i = 1 name = threading.current_thread().name while True: s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) s.connect((ip, 50020)) s.send('1234') data = s.recv(20) if data != '1234': print "Client: Received invalid data" s.close serverT = threading.Thread(target=server) serverT.start() clientT = threading.Thread(target=client) clientT.start() # This second thread may trigger the condition faster clientT = threading.Thread(target=client) clientT.start() Please debug and fix your kernel modules such that they do NOT cause the system to completely lock up.