Update:
I attempted top transfer files again with the WDTV on and not just in stand-by and mapped the share using the network name. After just over 10Gb of data transfer, connection lost.
Restarted the WDTV and as you suggested I mapped the share using the IP address and not the network name. Transferred 25Gb without problems, maybe that is the answer to network sharing problems? It would be interesting if you could map windows shares on the WDTV using IP addresses. That is the way it works for the Linux shares so is that significant?
Further testing in the morning. 
