Re: FAILED: An error occured while opening a virtual disk. Verify that the Converter server and the running source machines have a network access to the source and destination ESX/ESXi hosts.

Seems like port 902 are blocked:

2014-08-09T15:00:25.984-04:00 [10288 warning 'Default'] [,0] [NFC ERROR] NfcNewAuthdConnectionEx: Failed to connect to peer. Error: Failed to connect to server 10.70.64.84:902

2014-08-09T15:00:25.984-04:00 [10288 info 'Default'] Sysimgbase_DiskLib_OpenWithPassPhrase failed with 'NBD_ERR_NETWORK_CONNECT' (error code:2338)

Take a look at this KB article for required ports: VMware KB:    Required VMware vCenter Converter 4.x/5.x ports