Can ethernet, can't ping

I have a new Dimension 3000 (XP sp2) which connects fine with the internet but what I want to do is connect directly to a robotic motion controller (with a crossover cable, yes that's been checked) which it will not. I took down all of the firewalls, I think (Windows Firewall via Settings and the Mcafee firewall and antivirus) and I still cannot connect or ping it or even ping itself (ping localhost, 127.0.0.1, etc). I have enabled incoming echo requests and put back the firewall to connect to the internet. I cannot ping anything (or be pinged which should have been enabled but that's maybe another problem). I even connected to another PC (running XP sp1) with a crossover cable, took down the firewalls and can ping the new PC with the old, but cannot ping the old PC with the new. I did a system restore to when I took it out of the box 3 weeks ago in case anything I did initially could have affected settings and the situation remains the same.
I have read through the "Ping:transmit error" thread from Eric (3/17/05) but I think my problem is different. Obviously some kind of networking is working since I can access the internet, but I am unable to do other types of communicating.