As the group was approaching the CDC, in the sandbag enclosure to the right there appeared to be a DShK Heavy Machine Gun on a tripod. As this weapon was built & fielded by the Soviet Union & other Eastern Bloc countries, chances are pretty good that the US troops guarding the CDC as civilization collapsed around them would not be using it.
The tanks seen outside the CDC are Chieftain Mk.10s, a British MBT (Main Battle Tank) designation FV 4201, manufactured by Leyland and used by the British Army between 1966 and 1995. This make of tank was never in service with the US armed forces. As such, it would be highly unlikely to see any abandoned in Atlanta as depicted. They have simply been painted tan and feature the inverted black "V" used to identify Coalition troops during the First Gulf War.
When in front of the CDC British Centurion Tanks are visible whereas the U.S. military uses Abrams which were correctly visible earlier in the series.
When the group is heading towards the CDC, the Winnebago starts to smoke and they stop. Shane says he will go ahead into the city and try to find a matching hose for the engine, as the one they have is shot.
But then they pull Jim out of the vehicle and lean him up against the tree. When they are ready to leave him behind, they climb back into their respective vehicles, and the Winnebago starts without a hitch and they drive away without any more mention of car troubles. However, this is because it's edited awkwardly. Shane and T-Dog left when they did and came back with the needed supplies before the decision was made to leave Jim behind, but no further time or mention is devoted to this supply run between/after these scenes.
When Andrea is sitting by her sister Amy's body, you can clearly see Amy breathing.
When Andrea is sitting by her sister's body, and Rick goes over to talk to her, she draws a handgun on him. She visibly doesn't cock the gun as she draws it, but the racking of the slide is still heard.
As the Winnebago turns onto the main road, a crew member is seen in the windshield's reflection.
When Dale Horvath is talking to Andrea about his late wife over the body of Amy their is a dead walker in the background breathing.