Update1:
I have acquired another C64 250425. Same result.
Update2:
I borrowed a C64C. Same result.
Update3:
I successfully flashed the RR-Net MK3 with the "alternative" firmware which I downloaded from http://wiki.icomp.de/wiki/RRNet.
With the new firmware, CodeNet starts and displays network activity on the screen, as long as the network activity is not directed to the RR-Net (192.168.1.64).
As soon as I send anything to the RR-Net, it displays the packet on screen and hangs. RUN/STOP key does nothing. I have to reboot the C64 before I can try another experiment. I have sent several types of messages to RR-Net and they all cause it to hang:
1. Click WarpCopy "directory". Result is "no reply" and RR-Net hangs.
2. Click WarpCopy "send server". Result is "unable to send server" and RR-Net hangs.
3. type "ping 192.168.1.64" in command line. Result is "request timed out" and RR-Net hangs.