The quest ended due to an unkown error

Exactly what the previous poster said. This glitch seems to only occur if you try to do anything regarding with Agent E in El Nath. But all other towns I've tried it seems to be perfectly fine. It's only in El Nath that this happens. I was a little baffled by it too, at first, but then I went to Herb Town on my way to Mu Lung, and talked to her again, and all was fine.

And lulz at half the towns marking the Agents and other event NPC's at one spot, when they're in a completely different spot. I think it's just to confuse us of their whereabouts. Afterall, they are sekrit agentz.