I was getting the error coming up when I either tried to macro-skill or manually directed the sim to skill via the bookcase. I double checked and it was for all skills except mechanics, cooking and cleaning. I hadn't in the past ever used it for logic or creativity so I didn't realise there was a problem with them.
After reading your post I decided it was probably easier to divide and conquer so I should stop procrastinating. I went through my folders dividing them by half and half again until I could get it to not occur, rather than just looking at the usual suspects. This took me so long that after I narrowed it down to couple of sub-folders I decided to just dump them. The folders contained houses that I had d/loaded pre FT so maybe something snuck in there that wasn't a problem until I installed FT.
I do appreciate you looking into it for me though