When the vampire Lestat first changes Louis he floats him above and drops Louis into the Mississippi. The ship beside Louis when he emerges is ironclad. The movie claims this happens in 1791, but ironclad ships did not come into use until the mid 19th century, with the famous Monitor v Merrimack marking a turning point from wood to steel in naval warfare.
Paris was surrounded by the German army on September 20th 1870, until January 1871 due to the aftermath of the Franco-Prussian War. This was an obvious danger after the defeat of the French army on September 2nd. No-one in Paris, however, seems to notice.
Louis tells his interviewer that he saw the sun rise for the first time in 200 years when he watched his first movie. It is implied that Louis saw the movie when it was new, or almost new, in the late 1920s, when he had been a vampire for less than 140 years.
Louis comes back to New Orleans (after years) to find a nearly mummified Lestat hiding in a graveyard. Right after the interview is broken off and the interviewer is riding off Lestat is in the back of the car; bites him and is back to his former glory instantly. A vampire drinking blood in the time Louis is in the old world would not be in this state.
In the very beginning, just before Louis begins his story, the shot from outside the window shows Louis' hair down. The next shot in the room of Louis' back shows his hair pulled back in a low pony tail.
In the middle of a movie, after Claudia cuts off her hair, she throws scissors on a floor. But in the following scene, after she screams when her hair grows back, she walks out and you can see her holding the scissors in her hand again, and with them she leaves the bloody cuts on Lestat's face.
In the scene with the two whores Lestat puts the one he hasn't killed in the coffin. Before he does so he throws the lid off the coffin, glasses in all. The lid lands completely on the floor, but in the next scene the lid is back on the coffin and Lestat is closing it over the screaming girl.
Three scenes show a sailing ship with hoisted sails while at anchor (on the river during the opening shot at Ponte du Lac) or at the dock (when Lestat first attacks Louis, and later when Louis and Claudia flee the city). No responsible sailing captain would have allowed that to happen.
After Louis becomes a vampire, his reflection is visible in a puddle of water in the cemetery: Although in Vampire mythology it is said that a Vampire cannot see his/her reflection, it is clear that in this adaptation a Vampire can see his/her reflection (In addition to the puddle, Claudia looks in the mirror after she has cut her hair and sees her reflection)
At the beginning of the film, we see Louis in the window of the hotel. When the shot changes to the inside of the room, it is from behind Louis as he is looking out the window at the city. If you watch closely, you can see that what Louis is looking at is actually a still image rather than the actual city, as none of the cars' headlights or taillights move and none of the other lights flicker.
The scene with the well where Claudia and her 'mother' are placed to be incinerated by sunlight is not possible in Paris, as the well is vertical. For the sun to shine directly down into it, it would have to be directly above their heads. This can only happen on earth between the latitudes of 23,5 N and 23,5 S. As Paris lies at the latitude of 48 degrees North, they will escape the sun (and live happily ever after).