Query - Date Criteria Problem

Hey guys, I really need some help on this problem.

I have a database for a tutorial center, and we have invoices recording the dates of the lessons that students pay for in this month.

We have a reminder form that display query results when today is the last lesson for the student so we can give them a new invoice. This has been working perfectly well untill now, it suddenly no longer displays the student and invoice for their last lesson.

What happens is, if there are 4 last lessons on Sept. 17, it displays reminders for 4 students in a datasheet subform. However, Sept. 17 may only be the second last or third lesson for some of the students. It just randomly shows a student that has a lesson on Sept.17, not their last lesson.

Thanks ahead to anyone who can offer me any advice.

SELECT tblStudents.StudentID, tblStudents.StudentName, Last(tblDate.dtDate) AS DateOfLast, tblInvoice.InvoiceID, tblInvoice.Paid, tblCourse.ShortDescription
FROM tblStudents INNER JOIN (tblInvoice INNER JOIN ((tblCourse INNER JOIN tblInvoiceDetail ON tblCourse.CourseCode = tblInvoiceDetail.CourseCode) INNER JOIN (tblDate INNER JOIN tblInvoiceDetail2 ON tblDate.DateID = tblInvoiceDetail2.DateID) ON tblInvoiceDetail.InvoiceDetailID = tblInvoiceDetail2.InvoiceDetailFK) ON tblInvoice.InvoiceID = tblInvoiceDetail.InvoiceID) ON tblStudents.StudentID = tblInvoice.StudentFK
GROUP BY tblStudents.StudentID, tblStudents.StudentName, tblInvoice.InvoiceID, tblInvoice.Paid, tblCourse.ShortDescription
HAVING (((Last(tblDate.dtDate)) Like "*" & [Forms]![frmReminder]![txtDate] & "*"));