I don’t believe I had a problem with the Security updates getting downloaded.

MSBA said “downloading security updates” for maybe 5-10 seconds and then it said scanning.

Everything ran just fine.

The OPs problem sounds to me like either like a Firewall problem or another of the avast! 6.0.1289 Windows XP SP3 related problems. I have noticed that a lot of the people posting a problem here are XP SP3 users using it with 6.0.1289. I believe Windows XP was just passed by Windows 7 as the most used Windows OS.

I wonder if Avast will even support avast! 7.x on XP computers? ISTM that there will be even more problems with avast! 7.x running on XP SP3 then there are with 6.x. JMO