I caught something while watching the episode where Locke and crew were returning from the Black Rock with dynamite.
During Locke's previous encounter with the monster, he stared it straight in the "eye" and it didn't kill him.
Now, after Boone died and Locke lied about it, it appears the monster wasn't so forgiving. It tried to pull Locke into that hole.
Could the monster be punishing Locke for the things he's done since being judged previously?