Hi Pondus and Safesurf,
Sorry for the delay in getting back as I spent last evening working on the issue.
Many many thanks for your help, problem is now solved.
I tried the Zone Alarm suggestion and it made no difference.
I then decided on the AVAST clean install as suggested but it did not work either.
Racking my brains I remembered that originally Zone Alarm had been installed before I discovered AVAST in the past. I could not see that this would make any difference but I decided to give it a try.
I removed AVAST with the remove facility in SAFE MODE and then rebooted to Windows. To be doubly sure I then manually deleted all registry keys related to AVAST. Not sure if this would matter though.
I then removed Zone Alarm with Windows add/remove as no vendor uninstall facility available and did the same with the registry.
Something else I decided to do was remove other items I have on my PC (for the time being at any rate) which I thought could be causing trouble ie Spybot, Trojan Hunter and Malwarebytes. Of the three Spybot sometimes seems to give trouble installing programs. I used to have it in the past and put it back on when I though I had a spyware problem.
I then installed Zone Alarm first and rebooted then I installed AVAST 7 and rebooted and Bingo I had the message to say that the virus definitions had been updated to 120715-0.
I decided not to get too excited at this stage until I had more proof but shortly after running up this morning I heard that very welcome update message and AVAST has updated to 120716-0.
Your help has been most valuable guys and many thanks again.
I was getting most worried thinking I had no proper protection against viruses.
Any feedback on what I did above would be most welcome and I guess could help others with similar issues.
Kind regards,
Greg.