find the spell in world.cpp and comment it out ....
OR even more simple use the spell_disable table ROFL
its in latest dbstructure so... 
hint:
Code:
/*Table structure for table `spell_disable` */
CREATE TABLE `spell_disable` (
`spellid` int(30) NOT NULL,
`replacement_spellid` int(30) NOT NULL
) ENGINE=MyISAM DEFAULT CHARSET=latin1 COMMENT='Spell System';
/*Table structure for table `spell_disable_trainers` */
CREATE TABLE `spell_disable_trainers` (
`spellid` int(30) NOT NULL,
`replacement_spellid` int(30) NOT NULL
) ENGINE=MyISAM DEFAULT CHARSET=latin1 COMMENT='Trainer System';
source: http://mmoforge.org/svn/ascent/trunk..._structure.sql
grtz