well IMChO stands for International Mendeleev's Chemistry Olympiad. Before 1991 it was All-Soviet Union Olympiad. Participant countries as u've understood are post USSR countries. This year it was 38th and was held in Moldova, there were 14 participating countries including Bulgaria and Romania (first time) which as you know are not from USSR. Organizator of the olympiad each year is Moscow State University. This year for the fist time there was English version of tasks. I think Theoritical part of this olympiad is much more hard than that of IChO and there's no any preparatory problems. If you know any Russian you can read about it in http://www.chem.msu.su/rus/olimpiad/olimp2004/welcome.html
Russians have got one outstanding student. He did 130 pionts in theory, while Putau had only 104.
By the way; may be in approximately a week I'll be able to post some problems from it.