Hi Aric, thanks for your reply.
I have had this set for several years now and this problem only occurred today.
Have tried disconnecting etc as in your first comment, several times, no success.
In answer to your second comment. Yes the TV buttons and the remote give access to the 'menu', 'volume', and if you mean the program information or 'EPG' button for 'Input'. I can also scroll through thses functions
Thanks very much for your help. Invoking the default setting procedure has solved the problem. Much cheater than buying another set!