vista pc on network drops xp machine

I have two vista home premium laptops(Satellite l 300) that are wirelessly connected to a D-Link router with a XP SP3 machine wired with cat 5. and an old satellite a35 laptop with xp sp3 also wireless. I have set up sharing on all macines. the xp can get to both vista machines no problem. the newest Vista laptop looses conectivity to the xp machines, but not the internet or the other vista machine. I tried turning off ipv6 and the 2 link layer topology mapper options in the wireless proprties as mentioned in this forum before. The older vista laptop did the same thing until I did that, but the newest one still drops. Again, I don't loose access to the internet or the other Vista machine, just the XP machines. Any thoughts would be appreciated