problem connect wireless connection before user logon in WXPSP2

Hi,
I configure, in a Windows XP SP2 within a domain, a intel pro wireless
3945abg, with Wireless Zero Configuration for windows XP service
(uninstalling the program Intel Pro Wireless).
My problem is often the connection lost, and this connection not
connect before user logon.
I have ping to computer, and when the computer initiate, four pings
are correct, and next pings are incorrects before the user loggin the
computer.

I can help, please...
I use a access point Cisco Aironer 1100 series, with open
authenticacion WEP of 40bits.

Thanks.
Angel Moreno.
Castellón, Spain.