It still sounds like the FRC port traffic for the Driver Station is being blocked (or the port is locked up) by something on the Win7 machine (for your own security, of course).
You might scan from another machine to see what ports the Win7 machine has open using something like
Angry IP Scanner
You've already eliminated the usual culprits - Windows firewall, anti-virus, extra NICs, intermediate router firewalls.
No other network related applications on the Win7 machine?
Perhaps booting Safe Mode with Network would eliminate the possibility of a third-party driver causing the conflict.