ETA: Since no one has answered my question I've edited/deleted so that it doesn't come up in a search of my site name.

That MSO... you mentioned indicates that you pasted from MS Word. Try re-creating the affected posts by deleting their contents or the whole posts, then copy from Word again but paste into a text editor first, then copy from there and paste into WP. Format inside the WP editor. Do this for all posts that contain anything with mso