"In order to reproduce, replicators consume energy." (Prolegomena, pp.6)
Given that the amount of available energy is always finite within an individual host, different replicators can get into conflict within individual hosts.
Take, as an example conflict between the memetic complex called "catholic doctrine" and gene-determined organic nature of an average Jesuit missionary.
Or a fanatic which willing to kill himself (and/or other people) just for the purpose of getting his lethal meme into media.
Or a conflict between conservative / liberal, left / right, carnivore / vegetarian memplexes etc.