When we played them the first time, the Packers were 3-1 with the only loss being by 3 points on the road against the Vikings. If they had beaten the Cowboys in Green Bay, they'd have gotten off to a 5-1 start (they beat the Bears the following week). The biggest reason they weren't the team then that they are now is that we beat them then.
After their 4-2 start, they lost four in a row, all to teams with top 10 offenses (Falcons, Colts, Titans, Skins). In fact, that's a pattern with them. They struggle against good offenses. They have 11 wins against offenses whose league rank averages to 22nd, and 6 losses against offenses whose rank averages to 6th.