dhcp timeout on a wireless connection

have got a mostly functional wireless infrastructure - linksys access point
using wpa-radius / XP sp2 clients / IAS as radius server

however we intermittenlty get issues of connectivity as indicated by dhcp
event 1003 / netlogon secure channel errors in the event log.

this all looks suspicioulsy like the behaviour of EAP authentcation / dhcp
processes being independent along the lines of that documented in KB314994 -
which i assume to be incorporated in SP2 ??

what is 'interesting' is that when i get these 'failed' connection attempts
the radius server logs an authentication attempt by the 'Guest' account
which does not have dial-in permission

the client somehow 'works' itself and then proceeds to use the computer
account for authentication which succeeds, but not quickly enough, such that
the client in the mean time has attempted dhcp / secure channel
establishment

the client is configured with the authentication parameter of "authenticate
as guest when user or computer information is unavailable" set to unchecked.

it seems there are two issues here;

i. why the guest authentication is being attempted on an intermittent basis
given the above configuration

ii. why dhcp (and other network processes) are not 'waiting' for the
physical network (which includes the radius authentication) to be
established

TIA

GT