In the coffee shop scene, there are three customers to which Arthur attends to. When there is a close-up of one of the customers, the other two customers are no longer visible despite their chairs being in the shot.
When Victor & his hit-man came out of Ben & Arthur's apartment (with only Ben was in the apartment) in an attempted assassination. As Victor was walking to his car, a airplane background sound can clearly be heard, however in the next scene while Victor was unlocking his car, the sound is clearly gone.
Ben asks that since gay marriage is not legal in California, would they have to challenge the Supreme Court to recognize their union. The lawyer says yes, although the Defense of Marriage Act states that "No state (or other political subdivision within the United States) need treat a relationship between persons of the same sex as a marriage, even if the relationship is considered a marriage in another state."
When Ben is on the phone learning of his attorney's death, he is shirtless. The camera briefly cuts away to Arthur, then it cuts back to Ben, who has a sweater on. Ben could not have donned the sweater in the two seconds the camera was on Arthur.
When Arthur leaves the apartment to pick Ben up from the hospital, there is a Halloween poster hung near the door. In the next scene, when Arthur returns with Ben, the poster is gone, and a table that wasn't in the previous shot appears.
When Arthur is at the coffee shop, there appear to be three people sitting. However, the first extra is actually Loretta Altman, who plays Mildred, who then appears as the third person, in a speaking role, in the next shot.
When Victor shoots the attorney in her car, she falls against the steering wheel and grabs it with one hand. However, in the next shot, as Victor turns and runs, both of the attorney's hands are on the wheel.
Ben tells Tammy that gays can get married in the state of Vermont. This is not true; at the time of the film's production, Vermont only allowed civil unions and didn't allow gays to get married until 2009.
Victor is excommunicated from the Catholic church for being related to a homosexual; being related to a homosexual is not considered a sin by the Catholic church and an individual cannot be kicked out of his or her congregation over it.
Father Rabin claims that the church is afraid that Victor will transfer bad Karma and negative energy to the congregation through his association with Ben and Arthur. Karma is a concept found only in Indian Religions, and is opposed as a theological concept by the Catholic church. Bodily energies is a concept derived from the New Age movement, and is also opposed by the Catholic church.
Neither Catholicism or any other mainstream branch of Christianity teaches that murdering a sinner absolves them of their sins and permits them to enter Heaven, as Victor repeatedly claims and which Father Rabin appears to endorse.
The goof items below may give away important plot points.
After killing Ben, Victor makes a comment about how Arthur will get a million dollars from the life insurance policy that he set up for Ben. When the insurance policy was first mentioned earlier in the film though, Arthur said that he had set the insurance policy up for himself, and that Ben would get the million dollars if he died. There was never any mention of the policy covering Ben as well.
Victor shoots Arthur once in the front, and again then through his back several times during the climax of the film. When Arthur's body falls to the floor though, there isn't a single gunshot wound (entry or exit) anywhere on his chest.