The Explorer View is an excellent feature that is integrated with Windows SharePoint Services that allows a user to access a document library as if you were accessing a file system through a Windows Explorer window.
One of my co-workers was having a new issue with opening a SharePoint Document Library using the Action/Open with Windows Explorer option. He and clients were previously able to do this with no problem.
The error occurred only on client machines running Vista. The odd thing as noted in the error message was that the url to the site and library were changed. A \DavWWWRoot was appended to the end of url (this was not the name of the document library).
After various tests and looking online, I ran across a hotfix on Microsoft – http://support.microsoft.com/kb/945435/en-us. After requesting the hotfix, installing it, and then rebooting, the error was gone and Windows Explorer opened fine.