Right after Clementine removes the piece of glass from Lucas' leg, there are repeated shots of the bedroom door as the intruders try to get in. During one such shot the handle that had just busted off reappears, intact. In the next shot of the door the handle is once again missing.
When Lucas kills one of the invaders by the car and chases Clémentine and the others into the tunnel system, it is dark outside. Yet, a few minutes later they can see sunlight streaming in through an opening above them, and when Clémentine finally tries to escape through a grating it is a bright sunlit day.
At the beginning of the movie, the romanian teenage girl (Sanda), after locking herself in the car, is trying to call the police from her mother's cellphone. The number she dialed is 112. Except that, in 2002 (when the movie action is taking place), the police phone number was 955, the 112 (standard European emergency number) being introduced only at the end of 2005 / beginning of 2006.
Notice that the interior walls, doors, cupboards of the house are filthy and could definitely use fresh coats of paint, and the floors are equally dirty and not tiled or carpeted--certainly not a pleasant place to live.
When "They" (of "Them") first ring the house the telephone ringer is the classic European electronic bell signal from the last thirty years or so. However when Clem answers the phone the device clangs like an analogue phone would have sounded from the phones of 70 years before that. Then again, when she puts the receiver down, it clangs again like an antique phone.
When Clementine drives to the house a crew member (most likely cameraman) is visible on the car glass.