Hello, urgent problem....

W2K3 server, with CITRIX Presentation Server 4.0, Novell Client 4.91 NMAS
NICI, sec login 3.5 client.
NO MS SP 1, but all actual hotfixes...

Problem:

When installing ZFD 6.5 workstation agents, the system will not present a
logon gui after reboot. Can ping system, no RDP or ICA connection possible.
Can see only mouse pointer, no shutdown reaction when ctrl+alt+del.
Without ZFD Client, everything works fine. Problem is reproducible......
Can't find anything in knowledgebase or elsewhere.
"Funny" situation: when trying to install zfd sp1, the installation
procedure requires installed zfd 6.5 for update, but with this, the system
is "dead", as described !