I've always thought the phrase was "deep-seated" not "deep-seeded," but I've seen the latter pretty frequently of late (and right now in a student paper), so I was beginning to doubt my instinct. Curious to see how many of you know which is correct off the top of your heads - no cheating.
(Incidentally, while I was looking up the right answer, I discovered all kinds of fun stuff, like the plural of "oxymoron" and the word that describes redundancies like "PIN number." Bonus points for anyone who knows those!)