turns out the main culprit was DNS
since my network is strictly local and my sole server is also the DNS server
I didn't specify a DNS address when configuring WinXP
(the default is automatic discovery and with only one possible DNS server to connect to I foolishly assumed.....)
anyway XP apparently looks until it is satisfied that no Internet DNS is available (over a minute on my boxes) and then reluctantly logs in
now it logs in normally being forced to accept the local DNS server

A