(at around 1h 5 mins) During the Vegas scene, the laptop in the Umbrella tent is locked on to Alice, yet there's a display box containing Africa in the lower left corner. There would be no logical reason for the Umbrella operatives to keep a look out on Africa when they're busy with Nevada.
(at around 2 mins) The opening scene in which Alice is naked in the shower shows her with no makeup. Yet, upon wearing the red dress she is wearing red lipstick. Then, in subsequent shots she is wearing no lipstick again.
(at around 18 mins) When Alice shoots "Stevie" through the head with an arrow, there is blood splatter on the truck after he is hit. After checking the pumps, Alice looks at him a second time and the blood splatter has vanished.
(at around 40 mins) During the crow scene when the flamethrower is about to incinerate Carlos, the woman he is holding has her hand on his shoulder. When we cut to Alice in the next shot we can see the woman's hand slide down off of Carlos' shoulder and then reappear there in the next shot.
(at around 1h 21 mins) Towards the end when Alice enters the Umbrella HQ and releases a clone of herself from the water/orb, the clone then dies. She is shown laying on the ground with her left hand covering only her left breast, with her elbow resting on the floor. In the next shot, from above, her arm is covering both and her elbow is no longer resting on the ground.
(at around 56 mins) After the characters arrive in Las Vegas, they park right next to the Paris Casino's Eiffel Tower and the Venetian Casino. In reality, The Venetian is one mile up Las Vegas Blvd (The Strip).
In the beginning the crew including Alice head through Salt Lake City. The only way to get to Nevada through Salt Lake it to drive mostly north and head in through Wendover. Later on in the movie they talk about gas and how they need to go to Vegas to get gas. The driver said he had about 100 miles left on his truck. It would have taken over 100 miles to get to Vegas from where they were. It takes six hours to get to Vegas from Salt Lake City.
Alice uses Sony ICF-SW12 Shortwave World Band Receiver Travel Radio at the beginning of a movie on her bike. This radio lacks scanner function and frequency coverage to receive mobile bands (CB/UHF/VHF).
This means the only way for her to catch KLKB broadcast would be driving with one hand on the radio constantly turning tuning dial.
She wouldn't be unable to hear convoy broadcast call at all.
(at around 1h 3 mins) When Claire grabs a lever action rifle to shoot the zombie trying to bite Mikey, after firing several shots we see her grabbing more ammo to reload the rifle, however the cartridges (in addition to being obvious stage blanks) she grabs are rimless pistol cartridges, which would not work in a lever action rifle. Come lever action rifles are chambered to fire pistol rounds, but only ones that have rimmed cartridges, the action in a lever action rifle needs a extended rim to grab onto.
(at around 6 mins) After the Alice clone is killed at the beginning, her body is shown being dumped into a pit with the other dead clones. Even though Dr. Isaacs has been killing the clones for weeks, none of the dead bodies show any decomposition, nor have any of them desiccated (dried out) in the desert heat.
In the council chambers, Wesker's glasses reflect the room around him. This isn't a mistake - all council chambers are identical, and Wesker's holographic cameras would pick up the reflection of his table - as well as the reflections of the other holograms in the room during a meeting.
(at around 41 mins) After Alice uses her powers to kill the crows, Dr. Isaacs uses 3 satellites to locate her - as evidenced by the display on his computer monitor. Three smaller circles, presumably satellites, centered around a larger circle, presumably the radius of her psionic ability - even though we only see one satellite in orbit. Even if the satellites are not sensitive to psionic bursts (though they should be, since the AI in the Umbrella facility claims to have detected them), Project Alice has several implants which allow Umbrella to track and control her.
At the end of the movie, all survivors go to Umbrella HQ to get the helicopter. In fact it's very risky to bring everyone. Bringing noncombat personnel to that region risks the operation since they could have been killed or their presence decreases effectiveness of the heroes since they also should over watch the civilians. Since helicopter is a highly maneuverable vehicle it would be wiser to leave those civilians at a safe distance, go and get the helicopter and come and pick them up.
(at around 1h 27 mins) In the last moments of the film when the camera pans out showing the many clones of Alice. The footage of the awoken clone in the bottom left can be seen reaching the end of the recording and then played in reverse to fill a few extra seconds.
(at around 1h 26 mins) At the start of the final scene in Tokyo, there are rats in the street. As the camera descends through the street, one of the rats actually goes in front of the ground revealing that the street is actually a cut-away set.
(at around 18 mins) When Alice comes across the empty gas station she aims her cross bow at the attendant zombie "Stevie" using a basic reflex sight on the bow, yet in the scene it shows that she has managed to magnify all the way up to his chest revealing his name. The sight used on the crossbow does not have anywhere near that amount of magnification.
(at around 1h 7 mins) When Dr. Isaacs is held in a "secure room" the keypad used to release the door is quite clearly that of a cheap digital safe (the sort one would buy for keeping a few household valuables) and no attempt has been made to conceal the circular handle of the safe, the rest of which has been built into the wall.
(at around 40 mins) When the bus gets attacked by the crows Ashanti's character Nurse Betty has blood and dirt on her face. But after she locks the back door and she shoots the crows she is clean and there is no blood or dirt on her, then in the next shot when she dies she is bloody again.
(at around 1h 13 mins) When Carlos is in the big rig lighting up his joint, the camera pulls back and you can clearly see that one of the zombies reaching in for him only has makeup just past his wrist where you can then see normal human skin between that and the sleeve of his clothing.