Yuck. I did not watch most of that game, only the last 5 min or so, but what I saw was A) the Mavs are simply playing better and B) what i said about Kobe v. Dirk before is true. At the end, when being able to score was crucial, Dirk either scored or changed the defense enough for someone else to. Kobe did not and was not able to make the amazing play when it was needed.
Lakers are done for the year, they need a point guard, and to start finding an heir to Kobe. And a better bench. They don't need it blow it up but they do need some more talent.
Not sure where they can find heart though.