I have two nodes cluster runing windows server 2003 with SP2 and exhcnage 2003 with SP2.suddenly after installation ,the HTTP cluster resource keep failing. I un-installed mcafee virusscan enterprise 8.0 and mcafee group shield 6.2 and still the problem exist. After looooooooooooooooooooong searching i found that the problem is with windows server 2003 SP2 !!!!!! I found the solution,you have to run this to solve the problem: Netsh int ip set chimney DISABLED With this command the following registry entry will change from dword:00000001 to dword:00000000.HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Servic es\Tcpip\Parameters]"EnableTCPChimney"=dword:00000000 Without reboot all is fine. But after you restart the servers the connection with rdp and outlook is very slow with VISTA and OUTLOOK 2007.With Windows XP and Outlook 2003 it looks good. To update the NIC driver make no difference.