This problem typically occurs on Web servers that host Office SharePoint Server 2007. This problem occurs because of the configuration requirements of Office SharePoint Server 2007 when Kerberos authentication is used. However, the problem may occur for any kind of Web site that is using Kernel Mode authentication, Kerberos authentication, and a domain account as the custom application pool identity.
This problem occurs because of a bug in the HTTP kernel-mode driver (HTTP.sys). Refer to hotfix KB962943.