have this strange intermittent issue, on two separate occasions, on the same box spanning 2 entire scratch rebuilds of this machine, I can not ping a certain subnet, other than the router.
if I restart the network service on the computer having this problem, it all comes back online. I can however during the whole time reach the subnet and computers on it without a problem from any other machine.
Have you tried swapping the NIC? When they go bad they can do odd things like that. I'd especially suspect something like this if the machine's network configuration is vanilla. Just a thought.
Peter