At 11:00 PM on the night of the Millenium Heist, Gin says they will now gain one tenth of a second every minute until midnight to gain the extra ten seconds the heist requires. However, 60 minutes' worth of gains will only yield them six extra seconds.
When stealing the mask, Mac says there are "75 seconds" until the guard shows up. That time has long since passed as he says "35 seconds". That 35 seconds also passes LONG before the guard opens the door and sees the "Monkey". Apparently Mac can't read a second hand. Additionally, for Gin to place the monkey and escape that quickly without setting off the alarm is impossible, she would have had to complete her exit before the guard turned off the alarm and opened the door, to avoid being seen by him.
When Virginia is explaining to her boss the break-in to steal the Rembrandt painting, she quotes Mao Zedong (or Chairman Mao) as saying, "Let a thousand flowers bloom." The actual quote from Mao was to "let a hundred flowers bloom" referring to the Hundred Flowers Movement which preceded the Cultural Revolution in China.
After a brief car chase Mac pulls up to the curb and we see the car is heavily damaged on all sides; the damage is much more extensive than this chase caused. On the DVD there is a deleted scene of a much longer car chase that explains this discrepancy.
When Mack and Gin are robbing the bank in Malaysia and she puts on the goggles, the next closeup shot is not of her face. There are wrinkles on the forehead, and the eyebrows are drastically different from hers in the next shot.
While Gin is doing gymnastics on the ceiling beam in Mac's castle, there are three mailing tubes on the chair as Mac walks in. Without being touched, they change position after she jumps down, sits at the table and lowers her head.
When Mac and Gin arrive to steal the mask, the approach in a small boat wearing wet suits and enter the water wearing scuba gear. After the theft, Mac is waiting for Gin in the boat who surfaces in her wet suit but wearing no scuba gear. No scuba gear can be seen on Mac or in the boat.
When Mac and Gin are standing on the top of the castle's tower it sometimes has a very low parapet (e. g. when Mac approaches Gin from behind or when he throws off the glass), sometimes it has a high embrasure ("I never come up here without dropping something off"); the position of Mac and Gin to each other changes likewise. In the first aerial shot from the helicopter, the castle doesn't seem to have a tower at all.
When Hector Cruze and Chiel Inspector Yeng San enter the security room (where three guys are seen standing in front of computers), one of the men is wearing a blue party hat. The doors are then seen opening and that same man is seen taking off a green party hat.
The Petronas Towers in Malaysia are not located immediately beside slums. The scenes involving the hideout in Malaysia were filmed in actual slums, and the towers were added into the film later. The Malaysian government complained about this as they felt it misrepresented their rich/poor divide.
Kuala Lumpur is not in the Southern Hemisphere - it is actually a little over three degrees north of the equator. Being that close to the equator, it is always "summer", and the days and nights are very close to equal length all year 'round.
Gin tells Hector that for stealing the mask Mac will get 20 years to life for grand larceny, the crime takes place in the UK where such a crime would be non-dwelling burglary and subject to a maximum sentence of 10 years.
Malasya is located in the northern hemisphere. Although its small latitude, technically it would be winter, close to the solstice. Malasya local time is shifted more or less one hour from its legal time, so when their clock marks 6:30am, geographically it would be 5:50am. These two facts points that it would be dark at 6:30am in the beginning of January there.
In film, the banks go off line at midnight local time. Sydney goes off line an entire day before Kuala Lumpur. In reality, Sydney is only 3 hours ahead of Kuala Lumpur. Both banks should have gone off line within 3 hours of each other
In the train scene, Hector points his gun at Gin with his finger all the way inside the trigger guard, but behind the trigger, a position from which it would be impossible to fire. He has no intention of firing, and in fact would want to take no chance.
When Gin waits for Mac at Pudu Station at 6:30 AM it should be still dark (or at least dawn) outside. Malaysia, being in the southern hemisphere, actually has longer days around the New Years' celebration due to the fact that it would be summer there while winter in the US. Given that, it's perfectly reasonable that it could be daylight by 6:30 am.
When stealing the mask it takes Gin about two minutes to pass through the laser grid. When she takes the mask, Mac tells her there are about 30 seconds left before the guard reaches the room. When the guard finally reaches the door Gin has already vanished, but the laser grid is still active. Given that, it becomes easy to explain that, in getting to the mask, she would have been slow and careful, but not necessarily so when she retrieved it. Also, with the practice undertaken, it would make sense that, in real time, it would probably take her about 30 seconds or so to get through it, and just appeared to be longer to increase the dramatic tension.
When Gin is stealing the mask, she uses powder to reveal on last laser beam that Mac can't she because she is blocking it. However, if she had actually blown on her powder hard enough to get enough powder off to see the beam, she would have set off the alarms. This would be the case if it would have been normal foundation, however there is no consensus to the fact as it could have been a much lighter, and, therefore, not as likely to set off the alarms powder.
Gin uses chewed gum to neutralize the pressure switch while stealing the mask. This would leave her DNA behind. Some would argue that she was setting up Mac and would not care, but she was unaware that Mac knew who she was at that time. Her leaving DNA would mark her as careless and tip him off.