3Com Office Connect

The scenario…We have a 3com Office connect internet firewall router which is in front of 2 nt 4 servers all 3 with external addresses. The 2 servers are connected to the router through a linksys 5port workgroup hub. One of the servers
(server A) has been having problems being pinged from the internet(www.all-nettools.com). During this time it can ping the internet. The other server behind the router (server b) can ping server A and the 3 com router can ping server A. I can reboot server A and it will be alright for about 1/2 of a day to 2 days(you can ping it from the internet) So I have no thoughts on this. Any help would be appreciated. Thanks in advance…