Although this article addresses the inability of a chronic masturbator to ejaculate inter-vaginally, the same applies to those of us who become unable to erect and penetrate due to habituation to manual stimulation.

…Though women have a tendency to read too much into the intimate relationship between a man and his right hand, it rarely causes a problem. That is unless it develops into a compulsion, or a man becomes so conditioned to his own optimum brand of manipulation that penetrative or oral sex fails to provide him with sufficient stimulation to achieve orgasm.

Sex researchers call this phenomenon autosexual orientation. The term covers men who are reliant on a completely constant form of self-stimulation as well as those who get used to such an “idiosyncratic” style of stimulation that they disable their ability to ejaculate during regular sex. When the sex that you have with yourself is so perfect that you can’t translate it into sex with someone else, you have a problem. Dr David Goldmeier, a sexual dysfunction expert at St Mary’s Hospital, West London, says: “Some men who suffer from retarded ejaculation report that the combination of very erotic fantasies at masturbation, combined with high-level manual friction, enable them to climax in that scenario, but that vaginal sex is not so much of a turn-on, because the man does not get the same degree of stimulation and because the woman is not as erotic as their personalised masturbatory fantasy.” ….

Sex advice: is masturbation wrecking my sex life? – Times Online