The attached very simple PowerPoint document can be opened for example by
clicking on the file icon. However, when opened via UNO (in Java), the returned
proxy object is null.

OpenOffice.org gets startet with

  soffice -headless -nologo -norestore -nocrashreport
accept='socket,host=0,tcpNoDelay=1,port=8100;urp'

The used method is 

  desktop.loadComponentFromURL ( "private:stream", 
                                 "_blank", 
                                 0,
                                 properties );

with the properties
  ReadOnly=true,
  UpdateDocMode=0,
  MacroExecutionMode=0,
  Hidden=true,
  InputStream= (an adapter object containing the bytes from the file)

The same method works flawlessly with a lot of other PowerPoint example files I
have, but not with this one.