IIS and other services

We have a DNS/GC/Exchange server up and running. The IIS service stops about every 2 hours, then affect the services that need IIS ,POP3 and IMAP stops also. I can restart them and everything is fine for a couple of hours.
First comes to mind is Code red, however no other indications on this. Event log shows an error with the Net Time setting then immediately goes into stopping the services.
Any Ideas?