Losing network connection

I have 2 windows 98se machines connected to a Win XP Machine. Usually when
initially booting up both machines will logon to the network just fine,
however the windows 98 machines will for no reason drop the connection at
which time I have to renew the IP addresses manually. Rebooting will not
help.

What could be causing this and how do I fix it.

PS. this is a wireless network with a Dlink router and cards.

Thanks
Shawn




Shawn