Are you under the impression nobody had any problems with the Witcher?
How did the fight with the demon go? After he runs off, as soon as you take the elevator up to the throne room a cutscene should be triggered showing your character, then panning around to show the room, the camera moves up to Laiken on the throne, and a conversation should then automatically start.
FWIW, I've never heard of this happening before. A couple people did run into a problem where the cutscene with the demon running away wouldn't get triggered. One tried different conversation and combat combinations until one worked, and another reported that if they avoided mindreading Sassan before the summoning, the cutscene proceeded ok. A third person mindread all 3 involved to get past the cutscene.
Have you reloaded and tried different options with Sassan (heal, summon or attack), etc, before heading to the throne room?
If it is a problem with that particular cutscene, maybe a clean reinstall of the game could help.
If you have access to a different system, you could try your save there and see if it works.
Try emailing firstname.lastname@example.org or email@example.com.
In XP the saves are in the folder
C:\Documents and Settings\ %username% \Local Settings\Application Data\Divinity 2\Savegames
or in Vista / Win 7
C:\Users\ %username% \AppData\Local\Divinity 2\Savegames
You may need to set Windows Explorer to show hidden files and folders (XP, Vista
, Win 7