How can a bank hold a lien on my truck after sending me the vehicle title?

My used 2003 truck has been paid off in January of '06. I received the title and a letter congratulating me that my installment loan was paid in full. So yesterday, I checked my credit report and it says my installment loan account is still open and I still owe money on the truck. Today I called the bank(Fifth Third), and they said I owe money and even though I have the title, they still have a lien on my truck. Also, they are saying my last payment was returned for insufficient funds, but when I went to MY bank, MainSource, they were saying that they were never notified and have no records of any check coming back to them. I paid my truck off in 1 year, and Fifth Third sent me the title and now want more money. How can they do this, and how bad is this hurting my credit? Thank you in advance.