nothing wrong with your d2, something disturbs the communication between nas and PC, are you using a wireless connection between pc and router ? If yes this can be the cause of transmission abort. Use a wired connection.
Second what does the tftpd32 window shows when you try uploading the image ? and is there any data in the log viewer of the tftpd32 server ?
If auto upload goes wrong we could try to do manual loading step by step but if uploading of the kernel fails very likely you also will get problem to upload firmware files. So first we should solve the communication problem