Russian Language UTF-8 PROBLEM - Joomla 1.5: Установка и обновление

Hi all,
I have a problem with Joomla russian language.
On all browser Joomla display correctly except Mozilla Firefox.
But when i open the site with Firefox the charset of the browser changes automatically from Unicode (utf-8) to Windows-1251 and i see the site with strange chars �аОаЕаВаИаК.
The site with the problem is http://www.tipfilm.com
How can i repair this bug?
I saw other russian language sites made with Joomla and everything shows without errors.
Thx.

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4. Languages spoken at the conference - Russian.