For this issue, we recommend to contact the firewire adapter support. In the meantime, we'll try to fix your network connection problem.
The only odd thing is, the entire system was working fine, for years, until I installed the Intel Ethernet card.
I will eventually continue with the firewire driver research, but for now, I have to turn the PC over to someone else for a few months and they won't be using the Intel Ethernet card.
This item can be closed.
System changes during installation may have affected the card. Should you find anything, feel free to contact us.