Imagine that, another tax question (student loan interest)

Sallie Mae is stating that interest paid this year on a student loan is not tax deductible, due to the fact that it is a private loan. I call hogwash because the loan was used to pay for schooling. Sallie Mae issued a 1098-E for last year (2009), but this year is saying "Although you may have paid interest in 2010, it is ineligible for a tax deduction."

The interest paid this year is over $600. However, during a phone conversation, Sallie says this is a private loan and not deductible. Under what circumstances would this loan interest not be deductible? Since it is over $600, will there be a problem if I claim it without the 1098-E?

Lastly, I read that I can send them a W-9S to certify the funds were used solely for education expenses, which would make the interest tax deductible. I just do not understand how they issued a 1098-E last year, but this year will not, as I did not have to send them a W-9S last year.