The network configuration is interfering with Component Object Model (COM)/Distributed COM (DCOM) operations or the recording(s) that the Media Master control bar does not play are recorded in the G729a format.
Because the Media Master control bar relies on DCOM communication to communicate with the Cisco Unity server, verify that DCOM communication is enabled on the subscriber workstation and on the Cisco Unity server.
Verify that the AvCsMgr and AvCsGateway services are running as a distinguished Cisco Unity account (as specified during installation) and not the Local System account.
Verify that the subscriber has the G.729a codec installed on the workstation, and that the recording(s) are still not playing. If this is the case, refer to Cisco bug ID CSCeb21978 for more information.
Apart from the two solutions discussed above, verify that there is no firewall between the subscriber workstation and the Cisco Unity server. The Media Master control bar does not work through a firewall. Disable virus-scanning services and VPN Client software on the subscriber workstation, as applicable.