(See http://www.mantisbt.org/forums/viewtopic.php?f=3&t=4146 for details) Fix found by Mischa Diehm.
Consult http://www.mantisbt.org/manual/manual.installation.upgrading.php for details/hints on how to upgrade.
it is used by quite some projects now and fairly easy to use. thanks to xsa and aanriot for their feedback