It all depends on the definition of "solved". I doubt whether the same standards of "solved" were applied to computers as well as to the bees. If one is willing to relax the standards, TSP isnt that hard to solve on computers either. One such old solution is to simulate the dynamics of an elastic band that is attracted to the cities. http://www.google.com/search?q=elastic+net+tsp

It is not guranteed to reach the absolute minimum cost, and no point of the band may pass through a city location right away. But more often than not the band stabilizes at a decent solution. Would this be considered a solution of TSP in a computer science sense ? No, it is not even an approximation algorithm. But for practical purposes it may be good enough, and I think thats what the bees care about.

Statistical physics has answers to such problems if the standards are weakened to "solves it to within an _acceptable_ tolerance _most_ of the time". However, both the weasel words, "acceptable" and "most" are necessary. These tools may be applied to other biologically motivated solutions as well.