You are getting the TFTP timeout right? If not ignore me, or try it anyways.
Odds are this happened to you after a reboot, in which case what happened was, when your tftp service attempted to start, your NIC had not gotten an address yet, so it was set to 0.0.0.0. So now what you need to do is start your TFTP service, first stop the service with:
sudo stop tftpd-hpa
then restart it with:
sudo start tftpd-hpa
Then try a pxe boot again, I think you will see different results.