Problems with C110 & A110 Vtech Mirage Dect Home phones

Have strangely got the same problem - about the same time you posted this, but intermitently. I have isolated that the problem is in fact the handset itself, not the base unit. I eliminated a problem with the base unit by a) registering a different DECT phone to it. - The base still works fine. b) Leaving the handset switched off for an hour or so (press and hold the "OK" botton to switch off / on); then whislt it was working, registering the handset to a different base (Base 2). And guess what, after 30 mins the "BASE 2" message started flashing on the faulty handset.
So, if you already have an A110 extension handset, make sure it's also registered to base 1 and maybe try to get just the handset repaired via VTECH. (or just buy a new handset if they are available).