Demon realm bug?

[kidc]

I've gotten to the part in the demon realm where Shaduroth has killed Volgar. I picked up the relics, ran away a little and equipped the shield and the ring. I went back to Shaduroth and tried to fight him. He is just standing there and not doing anything. I freed Galdryn and we both are attacking Shaduroth and he is not moving and of course we can't damage him. Anybody experience this or hear about it?