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What happened in my situation was that their ask jeeves spider returned within the next few weeks, went crazy on most of the same sites, and soon afterwards the rankings returned.
More commonly, if a site in the top rankings on direchit doesn't get as many click throughs as the other sites around it, it will fall from the rankings. I recommend if feasable clicking you links once per day, or more often if you can rotate IP's and user agents, like surfing on a dial up connection. Just remember to dump you cookies between clicks :)