Device 'LTO3 - Server' unable to communicate with client error. (4046223)

Date: Apr 10
Product & Version: NetVault All
OS Version: All
Module & Version: N/A
Application version: N/A


Symptoms:
Trying to restore some files from a SmartClient (VMWare ESX 3.51i) to a Windows client. Every thing works fine, untill restarting the SmartClient.
Now you get the following errors:
1] Background 2010/04/19 12:19:40 301 Media SRVSAPHIRE Device 'LTO3 - SRVRUBIN:SRVRUBIN' assigned to job,positioning media 'BackupMig20100417' <Tape_Enteo>; to segment 4

2] Error 2010/04/19 12:19:47 301 Media XXXXXX Device 'LTO3 - XXXXXX:XXXXXX' unable to communicate with client 'XXXXXX'

3] Warning 2010/04/19 12:19:47 301 Media XXXXX No suitable media/drive pair available for job

We can see that the media is loaded and positioned ready for restoring the data and then the Smart Client has a connection problem whilst restoring the data to the Client. Then displays that the above media isn't available for the restore and not reachable by Plugin.
Checked for network problems from the NetVault Server to the Smart Client, NetVault Server to Client, Smart Client to Client or the other way round as well, by using the ping, nslookup and telnet commands. All had the correct results.