Steam version.
Save file: https://dl.dropboxusercontent.com/u/1499536/Welsh.rws
Mod list: http://imgur.com/a/wYfJ7
Error message: http://pastebin.com/zJPjrKwT
I can load the save and continue play without issues, but when trying to re-save (manually or autosave) I get the error message. No new save is created.