You have XP SP3, using Avast Free 5.0.677, Windows FW (I would suggest getting a third-party FW for something stronger and 2-way protection).
To confirm, you now can get manual updates but cannot get automatic updates? Otherwise, you can surf normally? Avast made some changes so that there will not always be an update as frequently as there used to be.
Can you tell me what you have your settings for the following:
1. Open the Avast GUI > Settings > Updates > Engine and Virus Update (what is checked off?)
2. Open the Avast GUI > Settings > Updates > Update Parameters (is any box checked off?)
3. Open the Avast GUI > Settings > Updates > Proxy Settings (what bubble is checked off - 1st - Direct Connection/No Proxy, 2nd - Auto Detect Using IE Settings, or 3rd - Proxy?)
4. Open the Avast GUI > Settings > Troubleshooting > is the last box checked or not (Load Avast Services only after loading other other system services)?
What other security software do you have on this machine currently or in the past (including antivirus, firewall, and other security software)? If you removed the software, how did you removed it -- vendor's uninstaller tool or some other way? Sometime other security software can cause conflicts (current or remnants from the past). Thank you.