Sharing Airport Over Ethernet -- OS X Problems?

[bobber205]

This is so weird. My mom has a new pc in her room that does not have wireless. I told her that we could run a ethernet cord from her computer over to her new pc and use internet sharing.

Well this would have worked, but as soon as a plug in the ethernet cable (sharing on or not), OS X seems to be unable to resolve any addresses. If I go to a local IP, it works fine. (But that takes no DNS)

Any ideas? I know I've done this before with no problems.
EDIT
If possible, how do I downgrade my mom's mac to a lower version of OS X?

 

[digby5]

You need a crossover cable if you're connecting directly from PC-to-PC - that is, no router. After both computers can see each other (crossover cable or with a router), you need to manually type in the mac's local IP address into the PC config's (in the gateway address box).

 

[bobber205]

The other PC is getting a IP address fine. It's OS X That is having problems.

Ethernet in = no internet
Ethernet out = internet