Hi Vlk,
I thought everything was fine until setting up some new computers at work today. All 3 are 64 bit XP Pro boxes with dual core Pentium processors. These are newly built so there is no prior security software of any kind, nor had any additional security software other than avast! been installed yet.
After installing avast! I was unable to install any Windows Updates at all. I have not experienced this with any prior version of avast! so I assume it is specific this build.
At my request Windows was not updated by the builder (I wanted to exclude some updates and he was unwilling to take the time to do this). The first update which gives access to the "new" update site (not so new anymore) downloaded but hung when it came time to install. At this point I was not able to even scan for updates - the Microsoft page kept referring to Error 0X80070020. The suggested work around for this error is to turn off the antivirus but I found uninstalling avast! was the only remedy. This occurred on all 3 PC's but I cannot duplicate it on any of the existing computers which also have v 4.7.892.
Since there were a number of updates (59 high priority and 7 optional) the downloads occurred in stages. On one machine I did try re-installing avast! between downloads to see if one of the updates would cure this, but the problem persisted to the end.