I got an error in MySql during converting my phpbb2 to phpbb3

hy!
i try to convert my phpbb2 forum to phpbb3 but i got this error you can see on picture below. what that means? please help! thank you!

 

Hello !

Thanx for sending PM for help to me

Can you tell me with which script you're updating database?

 

Do one thing

- Open databese in phpmyadmin-
- Find the table and set a default value manually

 

I have this errors now

General Error
SQL ERROR [ mysql4 ]

Incorrect string value: '\xC4\x87e' for column 'forum_last_post_subject' at row 1 [1366]

SQL

UPDATE phpbb_forums SET forum_last_post_id = 84133, forum_last_post_subject = 'Profesorske plaće', forum_last_post_time = 1244364507, forum_last_poster_id = 352, forum_last_poster_name = 'Adriatic', forum_last_poster_colour = 'AA0000', forum_posts = 1922, forum_topics = 19, forum_topics_real = 19 WHERE forum_id = 25

BACKTRACE

FILE: includes/db/mysql.php
LINE: 174
CALL: dbal->sql_error()

FILE: includes/functions_admin.php
LINE: 1640
CALL: dbal_mysql->sql_query()

FILE: install/install_convert.php
LINE: 1756
CALL: sync()

FILE: install/install_convert.php
LINE: 799
CALL: install_convert->jump()

FILE: install/install_convert.php
LINE: 203
CALL: install_convert->convert_data()

FILE: install/index.php
LINE: 405
CALL: install_convert->main()

FILE: install/index.php
LINE: 282
CALL: module->load()