DC 10.70 vs 10.72

I've started to use DC 10.72 and Ethernet is not working with it.
I'm using an RCM6750, with a program that's been working for about
a year. I compile with 10.70 and it works fine. Use 10.72, and no
Ethernet. There's a link light, but I can't get DHCP to work.

I've looked through the release notes and there is nothing obvious to
me that affects my application, but maybe I'm missing something.

Any ideas on where to look? 

Steve