problem playing wma [BNI Mediabox Portable Media Library - 118450]

hi. when i put mp3 files on my BNI mediabox, it plays them fine, then when i put wma files on it it plays them for a minute (60 seconds exactly) and then jumps to the next song. It does the same for every wma file and the files are fine. Any solutions? thanks for your help

Neither the box or the instructions say that this will play WMA files.