As difficult as it is to swallow, my feeling is that Yahoo submission is completely hit or miss (assuming you have an adequately prepared site in the first place). The percentage of sites they accept is steadily declining, and the few new additions I have checked have shown no consistency whatsoever. I just looked at a new one they added that was little more than an "under construction" page! You think someone knows one of the editors...?
I can only hope that the public begins to realize Yahoo's content is somewhat stale and forces them to make changes to address this problem, i.e. more staff and clearer guidelines. However, I doubt that will happen, as I myself use Yahoo more than any other SE, problems aside, simply because it tends to bring back the most relevant results, has the easiest name to type in, is quite comprehensive...
Maybe I'm just bitter because I can't get a site listed with them that has no apparent problems.