Cannot open exchanger control device ([2] The system cannot find the file specified)

You will receive this error from (among others) Data Protector if the D2D/Tape unit has gone offline, or is not reachable from the machine controlling it. Normally the Data Protector cell manager. In Windows 2008 server you can make sure that Windows is connected correctly via the iSCSI Initiator which you can find in the Control Panel.