First, make sure the DM24 has the latest operating system version OS3.0 or higher.
Then, you may need to update the firmware of the IFFWDM card, a download on the Tascam website available currently (November 2004). The original v1.0 firmware has some incompatabilities with sync with some of the newer DM24s. This firmware update should resolve the problems. It also caused no audio to return from the host computer.