I spent a few minutes converting all of their dates to ISO8106, and suddenly the report started working.
I can understand if one converts the format for the report output, since some of our executives are morons, and cannot understand a date if it does not match their desktop flip calendar, but I don't understand why they would convert them for internal calculations. Our servers store the dates in ISO8601. Well, most of our servers do; SAP does it differently in places because many of their designers ate lead paint chips as children.
In short, please don't mess with the dates that come out of Oracle, folks. They set them up that way for a reason.