Windows Server Update Services trouble

Hi, in my company we use the WSUS to give the windows updates to all
workstations running Windows 2000 Pro / XP Pro / Vista Business connected to
the domain. The major part of computers, saying, 2/3 is HP, the other 1/3 is
Toshiba. The problem is that the administrator frees the updates to the
machines, the users installs it when they shutdown because since they aren't
machine administrators, they can't see the yellow shield asking for updates.
Now the problem starts because some users start the machine and between 2
min 30 s and 3 min of network activity (through the network status) appears
an error saying something like this:

svchost.exe error:
The instruction refers to memory at 0x000000000h..... The memory couldn't be
read

If the user answers OK (or yes) (I can't remember now) the pc locks at 100%
CPU and needs to be restarted and after a few seconds I lost the
connectivity with PC when accessing remotely (even the pc is connected to
network) using VNC to make assistence to users. What I made normally is
instruct the user to restart the pc and say me when reaches the "Press
CTRL+ALT+DEL" screen and then I enter using an administrator account and
disable the network connection in contol panel and ask to user reactivate
the connection, since I lost connectivity. At last I ask to restart the
machine and enter with their account and wait 3 minutes to see it the erros
comes or not. Yesterday I have a machine that was dificult to trouble
because the error always appears. I try also disable the Net logon and
Secondary logon services and restart them.

When my boss (administrator) say that there are new updates I went to home
at the end of working day thinking how I will solve and how many users will
be in trouble. Much users don't want install updates to avoid the problems.

There is a patch to correct this behaviour?

In my home I have computers connected in a workgroup and retrieve the
updates from internet and from time to time I ran the windows update to see
all updates and I don't have this problem.

With best regards,
Looksmart5000