Ben,

If you have link lights on one machine then you have link lights on the other. I hate Sun for not putting lights on their ethernet interfaces.

What is the output of "ifconfig -a" for each system?
What is the output of "ping (sparc IP)" from the PC?
What is the output of "ping (pc IP)" from the sparc?
What is the output of "netstat -r" for each system?
What is the output of "netstat -i" for each system?

Mail the output from each of those commands to the list and we can help.

Dusty