To isolate problem, I installed updates separately, one by one.
As I expected, KB2467174 Security Update for MS Visual C++ 2008 SP1 Redistributable
caused problem described in previous post.
On Microsoft WWW, I found information, that this update apply for systems XP and up,
so not to Windows 2000.
I think, there is also error in Microsoft Update WWW page.
This software should not allow to install updates not suitable for older systems.
(in the past, everything was OK - this is first problem this type)
Anyway, please kindly developers to check relationship between Avast UI and KB2467174.