I have set up hundreds of 4-6 station Peer-to-Peers over the last couple of years. In all of these cases, I have always used TCP/IP as the protocol for the nics, which has to be there for DUN anyway. Never a problem. Yesterday, I spent 8 hours diddling on a miserable two station peer-to-peer. One mobo was 3 years old; the other was 6. I installed Linksys PCI nics in both. No conflicts; network set up perfectly with MS Client; file & print sharing enabled; bindings okay; specified IP addresses one number apart; same sub; same workgroup; etc. Stuff I've done over and over again. This network refused to send files over to the other, or to be able to access the printer or fire up a program. They could successfully ping each other instantly; but no way did file transfer take place. Brand new (known good) cat6 cables & 4port hub.
I switched PCI slots; reversed cards in each machine; uninstalled & reinstalled; removed the PCI nics and installed ISA 3Coms and reset the network up all over again. Even made love to his wife. This network refused to work.
After lunch AND dinner, and with me totally befuddled and about to give up; I decided to try changing the protocol to NetBEUI as a final last resort. What the hell; may as well try the slow peer-to-peer thing from W95 days. To my amazement, the network fired up and worked with INSTANT response.