Virtual Server fails to start, and you receive "An error occurred loading an XML document" error message

When you try to visit the Virtual Server Administration Web site in Microsoft Virtual Server 2005, you may receive the following error message. The message appears in red text at the top of the Web page: Additionally, you may see the following behavior:

• When you try to start the Virtual Server service (Vssrvc.exe), you receive the following error message:
  The Virtual Server service on Local Computer started and then stopped. Some services stop automatically if they have no work to do, for example, the Performance Logs and Alerts service.
• The Virtual Server event log may also contain the following error message:
  Event ID: 1066 Source: Virtual Server Type Error Description: "Virtual Server encountered an unexpected error, 0x00000003

This issue may occur when the XML parser encounters a problem on the local computer. Virtual Server stores configuration information in XML format. A local XML parser is required to read and to interpret this configuration information.

To resolve this issue, try to install the Microsoft XML Core Services 6.0 XML parser security update that is described in the following Microsoft Knowledge Base article:
If this problem still occurs, you can reregister the existing XML parsers. To do this, follow these steps:

1. Click Start, click Run, type cmd, and then click OK.
2. Type the following command, and then press ENTER:
   regsvr32 %windir%\system32\msxml6.dll
3. When you receive the "DllRegisterServer in msxml6.dll succeeded" message, click OK.
4. Repeat these steps for any additional Msxml.dll files that are located in the %windir%\System32 folder. For example, repeat these steps for the Msxml3.dll and Msxml4.dll files.