When running Ethereal, I can see the receiver making a broadcast looking for my PC. The message says something like, "Who is <PC's IP>? Tell <Receiver's MAC>". Then I see the the PC sending a broadcast, "Who is <Recevier's IP>? Tell <Ethernet cards MAC>". The order may be reversed, but that does occur.

That does imply that the Receiver got the DHCP data from the PC, otherwise it wouldn't be doing an ARP request on the PC's IP address.

Then I see UDP messages coming from my PC on port 18678 to the receiver's port 18678. Then I get the destination unreacheable (code 3 - invalid port) where the source is the receiver 18678 and the destination is the PC 18678.

That is entirely expected. Until the Receiver has found it's firmware on the PC, downloaded it across the network and booted from it there is nothing listening on port 18678.

If you don't want to post your Ethereal trace here then send it to me at [email protected] and I'll see if I can spot what it happening.