Commissions Overview: Authorized amounts applied to wrong transactions

I'm having a big problem getting any of the Commissions Reports (Overview, Authorized, Approved) to display correctly.

How to explain?

I have a small number of schedules. The bulk of them are eligible to be paid by Quota on Collections based on a single Class: New Sales. On the Commissions Overview Report, all numbers are displaying correctly in the Base Amount, Calc. Amount and Eligible Total Columns. So far so good.

Today is 2/19. I go to Authorize Employee Commissions, and I only want to Authorize those transactions that are Eligible through 1/31/2009 (prior month). So I enter 1/31/2009 into the Eligible Date field. The help says, "To filter the list of commission transactions shown, enter the latest sales eligible date you want to show." Makes sense. When I apply the date filter, the amounts in the list are adjusted correctly... the only items contributing to the totals for each Sales Rep are those that are were paid on 1/31 or earlier. Everything is still OK.