The actual error in the log that is causing the failure is
2014-08-27T01:27:54.380+01:00 [05216 warning 'Default'] [,0] [NFC ERROR] NFC_CANCELLED 2014-08-27T01:27:54.380+01:00 [05216 warning 'Default'] [,0] [NFC ERROR] Nfc_GetPutFile: Error inside NfcFile_Stream
Converter is using an internal protocol called NFC to transfer data from and to ESX datastores. This protocol is implemented in a component, that Converter is consuming as a binary. For some reason there is an error in this protocol while transferring the data. From Converter point of view this is a single function call - Nfc_GetPutFile(), which should return when all the data is transferred. Unfortunately there is no logging of the NFC component and we cannot imagine what could have gone wrong.
As a workaround I would suggest to try an older Converter version - 5.1.1 or 5.0.1 - there were some changes in the NFC component so there is a chance the older version (using the older component) to work better.