I am able to connect to the Alfresco server using WebDav on my Windows computer (using both /alfresco/webdav and /alfresco/aos), but am only able to edit files existing on the Alfresco server. I am not able to add files or folders using WebDav. When I try I get a Windows error of:

Is there something I am doing wrong with my connection? I am connecting to the online Alfresco trial (not installing Alfresco locally).
many thanks