Finding something positive in NBC's late-night mess is difficult, but it seems like the renewed rivalry between Jay Leno and David Letterman just might be that something. Once Conan leaves to count his money, Leno and Letterman will go back to sharing a time slot and battling for No. 1. Leno was pretty consistently No. 1 back in his Tonight Show days, but Letterman has had a taste over the past few months, and we're guessing he likes it. What Letterman doesn't like is Leno. He's gone after his former buddy relentlessly over the past week. His latest shot came tonight when he accused Leno of pushing Johnny Carson out of the Tonight Show. Harsh! Not to be outdone, Leno hit Letterman with this: "You know the best way to get Letterman to ignore you? Marry him." You can almost smell the hatred through the TV.