The availability of a new version is checked when an Internet connection is established, and every four hours afterwards.
Update files can also be downloaded from these pages if required e.g.
My thanks to Alan May 6 2012 for fixing my AVG update problem.
I had figured out that Zonealarm was the culprit but couldnt see any instances in the program control section of AVG installer being blocked.
Thanks again Alan for saving me a lot of time and trouble.