Dont know if this helps?
- Try and enable GUEST on both systems.
- Make sure connection and file sharing is enabled
- Make sure you have a shared folder
It sounds like the cable is working if you can see the other system, but there are cards out there that dont need a x-over cable, one such is in the xbox 360 that doest not need x-over to connect direct to another eth card on a pc.
The first thing i said usually fixes any of my sharing issues.
You do need to make sure that the one machine is fully booted up before you turn on the other machine too.
Like said, try giving the computer a manual IP address if all else fails.
Remember there is the network wiz too.