Can access home network 1 way but not the other

here's the deal. for work we have to set up a private network, 1 computer has 2 nic's in it, 1 which has a public ip. the other is a local ip. any other computer connects to the local network. our problem is with windows xp home, all computers have a static local ip of 192.1.1.* with all the same subnet, group and group name. all of them are logged on as the same user and pwd,

are problem is with accessing the network the main computer with 2 nics can access all of the other computers just fine, but the other subordinate computers can not access the main computer (access is denied, or can not find the network name) although i can ping any of the ip's at anytime. sometimes i can not even access the group from the subordinate computers. any suggestions??