I assume the sending application is a Qt application on the Power PC board.
The Power PC machine can talk to itself over a loop back interface, which shows that an IP stack is functioning.
You assume the bytes are making it to the wire because the QUdpSocket says they were sent (you do know that UDP is unreliable).

Have you any evidence that there are bytes reaching the wire? Wireshark or similar dumps? Do these dumps make sense, have the correct addresses etc.?
Is the receiver a Qt program too?
Could there be byte-order issues causing your receiver to ignore message sit is actually receiving?