What would cause camphor, a ketone, to produce a broad band at 3450 cm-1?

Melanie took an IR spectrum of her solid sample, camphor, through pellet sampling. To prepare the pellet, she ground the camphor finely and mixed it with the powdered spectral grade KBr that has been stored in the laboratory cabinet for quite a long time already. When she obtained the spectrum of camphor after taking a background scan, she was surprised to see a broad band at 3450 cm^-1. This is not expected of her sample because camphor is a ketone. What is the broad band at 3450 cm-1? What substance could in represent? What could she have failed to do in her sample preparation?