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Thanks
I would assume there is a lot of click fraud in your field.
They (Overture and some WW members) say that they have measures in-place to prevent this but I don't trust 'em. At least not 100%.
I usually don't deposit more money than I'm willing to spend over a few days time.
Given the competitiveness and high stakes of your keyphrase(s) space, you may want to consider hiring a PPC campaign manager.