Do you have the patch installed? See the appropriate support page for
DKS or
FoV.
There was a potential problem where certain main opponents could be missing. The patch should prevent this from happening, but if the problem had already occurred in your save, installing the patch will not fix it. However, you can email your save to support@larian.com to be fixed.
See Lar's post
here on how to send them an Xbox save.
With the PC version, 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).