Can't use signs after fighting Imlerith

[Riverdragon]

Can't use signs after fighting Imlerith

Unfortunately my last working save is right before the isle of mists and I don't really feel like back tracking that far. Any ideas?

 

[Avalos]

Try jumping in water and then switch signs. It should work again after that. I've had the same problem (not at that point in the game) and that fixed it for me.