Thank you for that.
I did as you suggested, the manual update and repair, and now have the desktop shortcut. A power dip would be highly likely in this area.
However, Avast is still highlighted in Start - All Programs.
As it doesn't serve any logical purpose to have it highlighted I get nervous in case something has gone wrong. I can live with it if it's something that has been included with the latest update.
I have scanned with Avast, Malwarebytes and Superantispyware and nothing was found.
Thank you very much for your help.
Update:
I just learnt something: Start menu options for 'highlight recently installed programs' was checked. I don't know what update or installation did that but I've now undone it.
Thank you for you time.
All ok now.