I’m using the latest version of Avast, 4.0.202 (downloaded it today), and an updated Windows XP Professional. When I try to do a boot scan, I get three dots, then something along the lines of “Unhandled exception 3221225477”.
Any ideas, or other info I can give you? I don’t see anything in the event logs about it.
This is a known problem, sorry.
It will be fixed in the next update. 
Vlk
Hi,
Am experiencing the very same problem with Windows XP Pro after avast update(s). Does this error have anything to do with the last Windows security update/patch (Q811493)? It’s a major headache for some machines–slows them down–and has been pulled by Microsoft because it’s so problematic.
How soon can we look forward to a “fix”?
Kamil
It doesn’t have to do anything with any MS updates, it’s just a bug ;). If everything goes well, an update might be released during the next week. Otherwise the week after.
BTW, version 202 has one more severe (new) bug – the avast! screen-saver does not work…
Sorry for this,
Vlk