Microsoft recently published a hotfix for resource exhaustion in the TDI interface of Windows 2008 in KB 961775. This resource exhaustion may occur when a third-party legacy Transport Driver Interface (TDI) filter driver is installed on the computer. TDI filter drivers may be used by some antivirus software.
961775 A Windows Server 2008 or Windows Vista SP1 system encounters user authentication failure and a large number of leaked handle for the system process when it is installed on a machine with multiple processors and TDI filter drivers are installed. You can obtain the hotfix here.