Long time to start RADIUS negotiation

Hay everyone,

I have strange problem. I try to set up MS IAS for wired LAN XP clients with
802.11x authentication on the switch ethernet ports.
I have the problem applying Computer GPO during PC startup. (Time interval
after "preparing network connections" and CTRL+ALT+Del erquest.)

I try to sniff packets and I discover that comuter starts Radius negotiation
after 30 seconds after "preparing network connections" firs displays.

Ping to target computer with -t parameter strats to respond only when
CTRL+ALT+Del dialog displays. normal behavior is to recieve ping responses
sooner even before "applying security settings".

I try to unplug LAN cable after user logs on and plug it in again to restart
RADIUS authentication process and again I sniff that first packet sent from
the PC side is after 30s.

Is it normal delay or do I have configured something wrong.

Thank you

Marek