Recently I encountered the following error when trying to remove the URL for a project workspace in PS07.  The situation was I took a backup of the four PS07 databases, restored them to a new instance of PS07.  since the projects still had the links to the previous workspaces, I wanted to remove them and create new workspaces.  When I tried to remove the URL I would receive the message “The information is not complete.  If you want to change the site address, provide both the server and the complete site path: /sitecollection/subsite”.  A workaround is to associate the project with a different existing Project Workspace.  Once this is done you can successfully remove the URL.