There seems to be a lot of people with this problem! Came across this post from someone who works for AVG.....
Double-click the My computer icon on your desktop (or open Start -> My Computer)
Navigate to the following folder:
Windows XP / 2000:
C:\Documents and Settings\All Users\Application Data\avg8\update\download *
Windows Vista:
C:\ProgramData\avg8\update\download *
Find the avginfoavi.ctf and avginfowin.ctf files and delete them
Restart your computer
.
Even if your Internet connection is working correctly, incorrect DNS servers may be filled in, affecting AVG update. This can be caused e.g. by some virus that was previously on your computer.
Open menu Start -> (Settings) -> Control Panel.
Double-click on Network connections.
Right-click on the connection you are using and choose Properties.
Double-click on Internet Protocol (TCP/IP) item on the General tab.
Please check (and modify if necessary) the settings of IP address and DNS servers according to your Internet Provider settings or choose the Obtain * * DNS server address automatically option.
Confirm the settings by clicking on the OK button.
Close the window.
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Most people gave up on AVG and changed to Avast which just updates itself without having to do anything.......everyone seems happy with it and it's Free!
http://avast.com/eng/download-avast-home.htmlYou
have to just register with them when you dowload,
then it automatically updates!