At the risk of being nit-picky, I’m a little concerned by your use of the term “NetBEUI over TCP”, the reason being that NetBEUI is its own protocol, and it should be “NetBIOS over TCP”, meaning that you should not have two networking protocols installed. If I’m just over-reacting, then please ignore this first paragraph.
Other things to check for are:
– TCP/IP Control applet, advanced button, check the WINS folder tab for consistency.
– Are all machines using fixed or DHCP addresses?
–If fixed, are all subnet masks the same?
– Are all machines members of the same workgroup?
– If you browse the “Computers Near Me” from each of the three machines, what discrepancies do you find between the 3?
– For any shared resources (folders in this case) have you checked both the share permissions and the security permissions – this is a common stumbling block.
– See if you can add specific machineuser names to the permissions, such as \BoxAUserA.
Write back and let us know what you find.