sounds like you have definately got some corruption somewhere.
I suggest you try deleting the files in the dynamic folders;
'..\Beyond Divinity\Acts\Act1\Dynamic',
'..\Beyond Divinity\Acts\Act2\Dynamic', and so on
These are temporary Cache files, and deleting them can sometimes resolve corruption issues. ONLY delete the contents of the "DYNAMIC" folders. If in any doubt, copy them somewhere else to be re copied if reuired.
If that doesn't work, you may try an earlier save, but how far back you will have to go is anybodys guess.
Is this happening at the start of a new act?