I to am experiencing this problem today, did you manage to find a resolution?
I was getting multiple tries to transfer the file via TFTP from the Linux Server doing the PUT command. It ended up being that the firewall (IPTABLES) was blocking the traffic back, so I just shutdown iptables via "service iptables stop" to get the transfers going.
Once done I restarted the firewall
service iptables start"
Hope that helps JOJO, although I know this is way late.
Did you get a solution to this problem?