Converting from YaBB 2.2

[ThorstenE]

you used the wrong version from our YaBB converter (yabb2_to_smf.php). use the yabb22_to_smf.php instead.
http://www.simplemachines.org/community/index.php?topic=249777.0

a short note: delete your SMF and re-install it before you convert.  the old converter drops some indexes from the database tables and this is an issue in future use.