I've mentioned this article in class a few times but haven't, until now, had the precise reference handy. A copy will (shortly) be on reserve in the CNES library:
R. Hexter, "What Was the Trojan Horse Made of?: Interpreting Vergil's Aeneid." Yale Journal of Criticism 3.2: 109-31.
Although this article is specifically directed to passages in Aeneid 2, it is also useful on the idea of puzzles within the poem generally--that is, as Hexter sees it, there are passages of the poem that are structured in such a way that they call out for interpretation. (Other examples are the hesitating Golden Bough and the gates of sleep passage, both in Bk. 6.)