Yamaha DTXpress/DTXplorer/DTXtreme

I've been having trouble getting DTXpress to play MIDI-files.
It plays everything but the drums. 
When I arrange a MIDI-song I use the standard channel 10 for drums but 
the DTXpress doesn't agree with me and sets up different channels for the drums every time I press play.
I use an older version of Cakewalk, but that souldn't have anything to do with it?

Help, please.
Sven-Arne Skarvik