Problem has now been resolved. I spent a lot of time with both your suggestions. I did what your Helpline link suggested and there was no change. I then attempted to delete my Yahoo toolbar and could not because the Yahoo programme could not be found.
I then downloaded and re-installed the Yahoo toolbar. After I had completed the installation, I closed and rebooted my PC. I then opened IE, went to a couple of web pages then I closed my IE. I have now done this a few times and the message is NOT appearing.
I now have the Yahoo toolbar which I do not need but I am not uninstalling for fear of going through the whole problem again.