Yes, Danil. It works your way !

> ...I debugged the process of reading file (file contents) and discovered there is no LanguageEnvironment for russian in the image. So Unicode class >> value: give probably incorrect result. Is that the actual problem?

Yes, this is definetely a problem - the mcz is not loaded correctly.
Here is what I did (basically the same steps you described):
 
MczInstaller installStream:
 (HTTPSocket httpGet:
'http://www.squeaksource.com/RussianSupport/RussianSupport-dao.13.mcz'
).

Seems like this packages was the key I missed.
 

Locale switchToID: (LocaleID isoLanguage: 'ru').

It executed cleanly - no walkbacks.

RussianEnvironment was not part of the base image (or etoys image or
any other), because I was not sure that the underlying infrastructure
is stable. At this moment I think I can take another look at it and
send a package which could be included into a base distribution (if I
get it right that LanguageEnvironments are distributed with a base
system).

Thank you very much for your help work and help.

I think it would be nice to add support for default system locale (as preference 'useLocale' in 'general' category allows to do). My Vista gives me locale with isoLanguage 'ru' and isoCountry 'RU' followed by some unknown symbol... Right now I have no time to solve the problem but I believe I'll consider it in few days.

--
Dennis Schetinin