A vampire cleric may become an ex-cleric if his deity does not accept evil clerics, but character can remedy this problem either by changing allegiance or by devoting himself to an evil cause or a source of evil divine power (selecting new domains if appropriate). A vampire cleric who could normally turn undead loses that ability but gains the ability to rebuke undead, and one who can spontaneously convert spells into cure spells now converts them into inflict spells.
Does the paladin get treated similarily? Does the positive energy of healing turns into inflicting wounds in his case as well? I am asking because one of my players is a vampire paladin, so he is unable to get healed, or rather harmed himself and must depend on the rest of the party.