The problem is to do with the priest casting sounds, the following files are named incorrectly:
CHA_SP01.wav transmutation should be CHA_SP08.wav
CHA_SP02.wav illusion should be CHA_SP01.wav
CHA_SP03.wav abjuration should be CHA_SP02.wav
CHA_SP04.wav conjuration should be CHA_SP03.wav
CHA_SP05.wav divination should be CHA_SP04.wav
CHA_SP06.wav enchantment should be CHA_SP05.wav
CHA_SP07.wav evocation should be CHA_SP06.wav
CHA_SP08.wav necromancy should be CHA_SP07.wav
changing these around fixes the problem, just in case anyone wanted to know!