Solved: macbook stopped connecting to 1 pc on home network

so i have a home network, including 2 desktop PCs and 1 macbook. when i first got the macbook, the network connections were AMAZINGLY easy as compared to the crap i went through to get the PCs to work. everything went great and i was able to access shared folders on my PCs from my macbook without any problems, even including external harddrives. then one day, the connections got lost and the macbook had problems finding the PCs. soon after, it would continue to see the PCs, but one of the PCs would never connect successfully. the 'connect as' option button would show up, although it would never again prompt for a username or password, and regardless of whether or not that was even needed, it would not connect again to this computer.

anybody have this happen before/have some ideas?

pcs are both running windows xp home and the macbook is on the newest os x, leopard.

many thanks in advance.