MS Project file with broken TFS connection info

Under certain circumcances the connection information in the MS Project file (name of the TFS server and of the team project) needed in order to synchronize the MS Project file with the WI information from the TFS goes out of sync. The Project file is perfectly valid but can not be synchronized anymore – “Choose Team Project” button is disabled.
The easiest solution for the problem I have found so far is to save the file as xml. It seems that the TFS connection info doesn’t get exported into xml, so when you open that xml file with MS Project, thus creating a new MS Project project and importing the data from the old file in the newly created one, you get the chance to choose the TFS server once again.    

[Update: Although the above procedure functioned, it wasn’t really elegant, to say the least. In this forum entry Yogita Manghnani describes a better way to disassociate a Project file from a particular TFS.]