If you copy the line exactly from the release notes when copying files from your PC to the radio, and you get the following instead of a success message, it appears a hidden character or similar may have been copied and is causing the TFTP program to not process the operations.

C:\>tftp -i 192.168.100.100 put idu_GigaPlus_v1.3.3.tar.gz

Transfers files to and from a remote computer running the TFTP service.

TFTP [-i] host [GET | PUT] source [destination]

  -i              Specifies binary image transfer mode (also called
                  octet). In binary image mode the file is moved
                  literally, byte by byte. Use this mode when
                  transferring binary files.
  host            Specifies the local or remote host.
  GET             Transfers the file destination on the remote host to
                  the file source on the local host.
  PUT             Transfers the file source on the local host to
                  the file destination on the remote host.
  source          Specifies the file to transfer.
  destination     Specifies where to transfer the file.

Please hand type the command instead of copying it directly. The structure remains the same:

C:\>tftp -i 192.168.100.100 put idu_GigaPlus_v1.3.3.tar.gz
Transfer successful: 11329438 bytes in 17 second(s), 666437 bytes/s

Also see TFTP Timeouts When Copying Files.