If i'm understanding this correctly, one of the mods needs updated or reinstalled. It's saying that something requested does not match something found. Which means item value mismatch, which very likely also means that your save almost ended up horridly corrupted. I hope you're keeping backups of your saves, because this was almost a disaster.
EDIT: To be very clear at what this thing is saying, it's saying that the game is trying to put an item into the save that i doesn't know how to describe. It's like trying to save a magical sword, new NPC, or something like that, but it has no idea what to call it in the save file. It's like meeting an alien, and you and this alien can call each other certain brainwave derived names for 10 years 'cause they communicate via telepathy, but the moment someone asks you what his name is you stare blankly, 'cause you have no way of conveying his name, and you know he would be offended by any name you choose.