wild_card,
Thanks, and nice job finding that. I took a quick a look at it this evening and let me say (for those who won't be looking at it) that IMHO the spreadsheet is layed out very well. It is comprehensive, complex yet easy to work with. A very good sign that I doubt many more, if any, other errors like you caught exist. However, it is complex and one little mistake could effect it a bunch.
I am not exactly sure who built it, but nice job to whoever it was!