I have the same problem as this - however I managed to work around it by:
Go to Brighthollow ground floor Add Hiravias to your party (fails, no sound effect) Add Hiravias to your party (succeeds, sound effect) Go upstairs in Brighthollow (succeeds)
However, other posters have said that this doesn't work for them - Hiravias can end up outside the map so be warned.
if I drop Hiravias from my party and attempt to go upstairs again it fails as before, but I do seem to be able to add him again and go upstairs reliably. So, I'll just have to make sure he's left at the keep for this purpose.
