On Windows Server 2008 and Windows Vista SP1 multi-CPU systems that’ve anti-virus or other softwares using Transport Driver Interface (TDI) drivers, running on machines with multiple processors, can eat all the system resources available to them. Software that uses WFP’ll not hit this resource depletion issue. Reports indicates that Active Directory user authentication, AD replication, MMC snap-ins for AD, DNS, or DHCP that’ll not open, general network connectivity issues, and slow or sluggish responsiveness of affected machines. Refer KB961775 for more details and hotfix. Or download SP2 for Windows Vista and Windows Server 2008 that pre-fixes this issue, warned Microsoft.