Have you ever had Zone Alarm on there before? Even if you stop zonelarm, it still runs and will block traffic.

Just for the hell of it, you might try deleting your NIC from the Device manager then reinstalling it when windows reboots. Maybe theres some setting thats messed up.

Also, I would double check everythin on all the computers, makeing sure you didn't accidentally transpose a number of letter somewhere.

This seems like one of those problems where the answer is right under your nose.