WWW service Disabled

for the past one week, i always have problem on some of my websites servers,
those servers are running Windows 2003 Server, which "World Wide Web
Publishing" and "IIS Admin" services disabled by itself. Those web servers
(Domain member servers) are released to the public.
Both services are set to "Automatic" in the "Startup Type". However, the
services was 'Stopped' and changed to "Disabled" by itself.
Could it be Denial-of-Service attack or any form of vulnerbity? I have
already updated all the windows patches