I am experiencing the same problem using Libreoffice to access a Webdav Alfresco Share in Alfresco 4.0.c. If I edit a file that has been created already, Webdav access works fine. But attempts to create a file or folder fail with a message that the 'file does not exist' (probably because the effort the create the file failed). There is no file created in Alfresco.
Can anyone provide any clues on how to fix this?