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. Castell=F3n, Spain.