Disappearing P2P Network

We have 20 machines running P2P (through hub) and have been having horrible difficulties getting “booted” off the network right in the middle of working with files. I have already performed the following troubleshooting:

1) TCP/IP on all machines configured to automatically get IP address. Gateway assigned to the internet connection (part of a t1).
2)No other protocols running.
3) Workgroup name is consistent on all machines.
4) Three machines configured to “enable” for Browse Master – all others disabled.

We do not have a true server, but do have one machine that acts as our server and is basically where all files are stored and accessed from.

Any help would be greatly appreciated!