The anti-paladin's touch of corruption is described as creating an infernal flame, which in turn can harm those around him or alternatively it can heal the undead. Last night my group was stumped on this when the resident anti-paladin (don't ask) tried to use touch of corruption to injure a vampire. The initial assumption was no, it was negative energy being channeled for the effect, but on reading the description the power doesn't refer to negative or positive energy being channeled, and the damage effect doesn't exclude anything from being affected (including undead).
As GM I ruled he could use it to damage the undead as well as heal, if only because what self-serving anti-paladin wouldn't use such a power to both benefit his undead minions and keep them in check with the threat of destruction? But despite my spot rule for it, I am wondering if there is an official interpretation on this, some errata I am unaware of, or other clarification.