A client computer cannot receive new updates or does not appear in the Administration Console when the computer points to a Microsoft Windows Server Update Services (WSUS) server. The WSUS server is running on a Microsoft Windows Server 2003 Service Pack 1-based computer. The Windows Update log may indicate that the client computer's connection to the WSUS server fails with a "0x8024400a" error code.
When you send a POST request to a server that is running Microsoft Internet Information Services (IIS) 6.0, IIS may send an "HTTP 100 Continue" response in the middle of the response stream. Sometimes, IIS incorrectly sends the "HTTP 100 Continue" response after IIS has sent the “HTTP 200 OK” response.
To resolve this problem, install the hotfix that is described in the following Microsoft Knowledge Base article:
923507 The HTTP protocol stack in Windows Server 2003 sends a "100 Continue" packet to the client even though the HTTP request does not contain an "Expect: 100-Continue" header
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.