WMP12 - trouble syncing WMDRM files to portable device.

I'm trying to sync an audio book to a Coby MP725-4G. It is supposed to
support WMDRM10. I can play the audio book under WMP12, and the usage rights
indicate that I have 2 syncs to a portable device.

The audio books can have a few hundred individual files. When I try to sync
a file to the device, it works just fine. However, now all my files report
that there is only 1 sync to portable devices left. If I sync another file,
it also works, but now the files all report 0 syncs to portable device. From
this point, obviously, I cannot sync anymore. I can listen to the 2 files on
the portable device and I can still listen to the entire book with WMP12.

Am I syncing incorrectly? Is this a problem with the DRM? Is this a
problem with the portable device?

I've never tried to use DRM'd media before, so I don't know if I'm doing it
incorrectly or not.

TIA