automatic updates service causes svchost 100% cpu

Hi there we have several different laptops, all newish and fully protected
from malware and viruses connected to different SBS domains, they are
unusable about 1 minute after logon and the svchost process uses 100% of the
cpu for up to 6 hours. The cause is the automatic updates part of that
svchost process, after disabling automatic updates the laptops run fine,
however this is not an ideal situation. this all happened from about the
17/18th of august. the only workaround seems to be to disable the automatic
updates service, and all the while the desktops on these domains are fine.
Any ideas ? thanks