'Synchronize Users to Contacts' function doesn't handle national characters properly in Joomla environment

There were several users defined in Joomla 1.5.8. with Czech national characters like 'ř', 'í', 'á' in their names. After installation of civicrm-2.2.beta2-joomla.zip according to the documentation, the 'Synchronize Users to Contacts' function was activated. It created new CiviCRM contacts, but with the names cut at the positions of those national charaters mentioned. When tried to correct the names via the CiviCRM contact interface they were updated correctly.