[trevius]

I am guessing the NPCs are buffing with Haste when the aggro happens. It is most likely due to this block of code:

spells.cpp

	// slow and haste spells
	if(SpecAttacks[UNSLOWABLE] && IsEffectInSpell(spell_id, SE_AttackSpeed))
	{
		mlog(SPELLS__RESISTS, "We are immune to Slow spells.");
		caster->Message_StringID(MT_Shout, IMMUNE_ATKSPEED);
		sint32 aggro = CheckAggroAmount(spell_id);
		if(aggro > 0) {
			AddToHateList(caster, aggro);
		} else {
			AddToHateList(caster, 1);
		}
		return true;
	}

There probably needs to be a check added to see if the spell is a buff or debuff or if the SE_AttackSpeed amount being changed is positive or negative.