Error message when you try to provide a URL to create a Groove Mobile Workspace for SharePoint: "ERROR: Groove cannot make a connection to URL because it cannot be validated as a SharePoint site" (922151)

SYMPTOMS

When you try to provide a URL to create a Groove Mobile Workspace for SharePoint in Groove Virtual Office 3.x, you receive an error message that starts with the following text:

ERROR: Groove cannot make a connection to URL because it cannot be validated as a SharePoint site.

If you are using Groove Workspace 2.5, you receive an error message that starts with the following text:

ERROR: Groove cannot connect to STS URL because it cannot be validated as a SharePoint Team Services Web site.

These general error messages will be followed by a more detailed error message, such as one of the following:

Unable to read site description information.

UNAUTHORIZED: You have not provided appropriate authentication information to perform this request.

In most cases that produce this error, the workspace creation will fail. In some cases, errors or conditions on the site may prevent Groove Mobile Workspace for SharePoint from reading particular lists. In this situation, you will receive an error message when Groove Mobile Workspace for SharePoint validates the URL. However, the workspace creation will continue.

MORE INFORMATION

To identify the cause of the problem if Groove Mobile Workspace for SharePoint cannot validate the SharePoint site, use the following methods:

Verify that the site is a Microsoft Windows SharePoint Services site or a Microsoft SharePoint Team Services site, not a Microsoft SharePoint Portal Server site. Groove does not synchronize with SharePoint Portal Server.
Verify your role in the SharePoint site. You must be an administrator or an advanced author, not an author, to extend the site to Groove.
On the computer on which Groove is installed, verify that you can access the SharePoint site by using Microsoft Internet Explorer.
On the computer on which Groove is installed, add a new list, add a document, and then add a list item from Internet Explorer.
Verify that the SharePoint site version is 5.0.2.3501 or a later version. This information must be gathered from the Internet Information Services (IIS) server's SharePoint administration page. Typically, you can access the administration page by using a URL that resembles the following:
http://Servername:2804/fpadmdll.dll
If you have an earlier version, apply all available Microsoft Office service packs on the computer that hosts the SharePoint site.
Check the version of Msxml3.dll. It should be version 8.20.x or a later version.
If you are using Groove Workspace 2.5, verify that the SharePoint Quick Launch sidebar contains at least one list.