Plot hole: Cole explains that the demonic power is driving Karen mad because she is human. Cole later has Paige infected with one to drive her mad. This doesn't make sense since Paige is doubly not human, and shouldn't be driven mad. In fact the Charmed Ones have had demonic powers before and were not driven mad, but instead turned evil.
Plot hole: Piper is initially skeptical at Phoebe's theory that the Evil Enchantress could be Paige in a past life, because Paige lacks the Enchantress' ability to summon the elements. However, Piper knows that in Phoebe's past life she had a pyrokinetic power, which she does not have in the present.
Continuity mistake: After Phoebe jump kicks a warlock and falls to the ground, there is a blonde woman standing next to them. In the next shot of the warlock, when Piper blows him up, the woman is gone. But all of the mortals had been frozen, so she couldn't have moved. (00:37:40)
Plot hole: According to Paige's "fairy tale" the witch ends up with the prince. If this is really a past life, the sorceress ended up with the prince in the Middle Ages. So why do they have to fix it? Everything was just going the way it did according to her fairy tale, and good magic was obviously still present in the world.
Plot hole: Leo suggests to Piper that they use their magic to scare Wyke into a confession. In Ex Libris (Season 2) it is established that they can't/shouldn't use their powers to punish the guilty - even if it means saving/helping an innocent. There's no way Leo would suggest such an immoral course of action.
Continuity mistake: Paige looks in the Book of Shadows and suggests that the demon they are looking for could be Belthazor, not knowing that Belthazor is Cole's demonic form. But we saw Phoebe making extensive changes to Belthazor's entry in the Book of Shadows in a previous episode, and the changes are not in evidence here. (00:01:40)
Plot hole: Phoebe and Piper seem surprised at the fact that a white-lighter can impregnate someone, because they are dead. Piper says "how does a white-lighter get somebody knocked up?", but when she went to the future she saw herself with Leo's baby, and Leo told her that he hadn't clipped his wings. (00:46:25)
Continuity mistake: After Phoebe has her premonition about Paige at Prue's funeral, demonic bounty hunters show up to "eliminate" Belthazor. We see the funeral hall empty where seconds before Phoebe's premonition, there was a line of people waiting to give their condolences to the girls, Victor, Leo and Cole. (00:12:20 - 00:13:10)
Continuity mistake: The name plate under the photo of Leo at the Veterans Association indicates that he died on November 24, 1942. Paige's research indicates that Nathan and Rick both died on the same day as Leo, but she later finds out that they were buried at the V.A. on November 22, 1942, two days before they are supposed to have died.