On a 2651XM router, after a few transcoding sessions are created in order to configure Xcoder in the Cisco CallManager Admin page in the Cisco CallManager 4.x with a High Density Voice Network Module (NM HDV), it returns the Device in use already error message.
This is a design limitation. On the NM HDV, it is not possible to configure both the Media Termination Point (MTP) and a transcoder. If a transcoder is to be added, delete the MTP from the Cisco CallManager Admin page and add the transcoder. Make sure to add the new transcoder to the same media resource group (MRG) as the MTP.