I have a similar problem.  My base hand set is programmed as #1 and I have programmed my other 3 handsets as #2,#3 and #4, however, set #3 keeps defaulting to #1 and has no dial tone.  In other words, two sets end up as #1.
Any ideas?  Are there too many sets?
                
 BryanH
                
 November 2009