Good call drfocus - re-enrollment as an insider. windows update seems to be able to trip on any of about 20 things (I got wq0 remedy text files, hence the estimate, it's a guess as you see); an iso decrypted from an esd that did download elsewhere has been my remedy of choice...
Edit: Although I wasn't getting the error here, I had that thing turned on. Now it's off!
If just one of the computers on "my own network" got something bad, it could potentially be uploaded to the rest of 'em if that's turned on during Windows Update.