Windows - Linux Wireless network connection lag

Hi all,
first of all excuse me for my bad english...
I've a lag problem with a wireless connection between a wired linux
server (connected in lan to the router, through a switch device) and two
other windows xp's pc.
The first pc is an amd based system, the other is an Asus notebook (A6VM
family) intel centrino system.
I've no wireless problem if I use linux to linux connection, this make
me think about a windows driver problem, isn't right? what else?
Then if i try to communicate, for example by putty from any windows pc
to linux server, I get annoingh lag time for the result, though a banal
ls command.
I try to disable firewall and antivirus programs from windows xp
machines, nothing's changed.
Remember that i've no problem if I try a wireless communication from my
notebook with linux OS to linux server

Router: NETGEAR DG834IT v2
PC1 NIC: DWL-G520+
PC2 NIC: Intel pro wireless
Linux server: generic realtek compatible (wired)