Could certainly be Finals' hangover...after all, it's not often a team gets to the NBA Finals, is favored to win, and is a 4th quarter and a 13-point lead away from taking a 3-0 lead, only to lose the next 4 games and the NBA title while watching a player from the other team parade to the free throw line throughout.
Of course, it's not as if any other traditional powerhouse teams are lighting the league on fire right now, either, so it's not as if Dallas is done. Spurs haven't looked fabulous, the Suns are struggling and the Clippers aren't playing great yet, either (although they played quite well for 36 minutes against Dallas).