Thanks both for that. I went on the Adobe.com forum and subsequently discovered that there had been a problem and from reading some instructions given to others I was able to do some jiggery pokery in Tools, Advanced etc, ticking a box etc and rectify matters. It had been terrible, though, causing adverts appearing and flickering all over the screen. It is heartening that people are there to help you in times of desperation and not all out to get you. I think Adobe messed up a bit for some with Adobe 10.3.14 or some such edition number.