Ok, see what you think on this theory, it just occured to me!!
When Locke first saw the smoke monster, think it was Walkabout, he said "I've looked into the eye of this Island... and what I saw was beautiful"
Is it possible that he saw the smoke monster as not a monster but Jacob and maybe instead of black smoke it was White, hence it being beautiful, he said he saw a beautiful bright light to Eko
Maybe Jacob wanted Locke to help him and Otherman realised this and so manipulated the events to make sure he could use Locke as a loophole. In Exodus Pt 2, the Monster attacked Locke and tried to drag him down the vent. Could this be Othermans way of getting to Jacob quicker? Killing Locke there and then but then re-emerging as Locke from the vent, apparently unharmed and then use Eko to get to Jacob? It didn't kill Eko the first time he saw him. I really wish I could understand!!!!