This issue may be caused by one of the following:
(1) The .wav file is encoded using Global System for Mobile communications® (GSM®).
(2) The BlackBerry® Enterprise Server is running BlackBerry Enterprise Server 4.1 SP2 or earlier or the BlackBerry Internet Service is BlackBerry Internet Service 2.2 or earlier.
(3) The BlackBerry Enterprise Server does not have Microsoft Windows Media Player® 9 to 12 installed.
(4) The Fraunhofer IIS MPEG Layer-3 codec is not installed or configured on the computer running the BlackBerry Attachment Service.
See details below: http://www.blackberry.com/btsc/KB13547