bt1100 again handsets and base?

My handsets have suddenly gone wrong; have followed darren's advice, won't accept pin.One handset out of 4 shows it is 4; one showed it is 3, but now, along with another one has a blank screen but the little red call light is on, won't go away if I take batteries out and put them back. The other one is flashing not reg but won't reg when I go through the system. The one that says 4 rings and people can hear me but they are faint. Can someone please help before I THROW them in the bin and faint myself?