I had tried one similar, but ran yours with and without modification of the IP address, and get back:
Starting w5100
0.0.0.0
After the original post I stumbled across a video blog talking about an NKC board that was "not compatible with the MEGA". NKC was the distributer for Amazon on the boards I purchased, but those were clearly different as the chip & RJ45 were on a separate daughter card. In any case, it would appear that boards using a reference design before the MEGA was released might have a problem. Even the description of the official R3 says the prior revision was not compatible as the SPI bus was moved.
If I define 11, 12, & 13 as input can I jumper 50, 51, & 52 to those without damaging anything?