Outlook syncing with iTunes or ACTS

A user's Outlook seems to be syncing with iPhone, iTunes or ACTS. Sometimes, Outlook calendar events either get missing or show incomplete information. How do I know if a user's outlook is syncing with any of these? ACTS was once the contact management software in the company where I work, but they had already switched to Goldmine 6.5 a good while before I joined. This is for Outlook 2003 and Exchange Server 2003. The user has an iPhone 3G that does over-the-air syncing with Exchange. The iPhone syncs with iTunes on her laptop computer, which is also her work computer that contains her outlook. I noticed a server error message as seen below on my email server today:

Event Type:      Warning
Event Source:      EXCDO
Event Category:      General
Event ID:      8241
Date:            4/17/2006
Time:            4:24:36 PM
User:            N/A
Computer:      <server>
Description:
An existing appointment with the subject "" in mailbox <mailbox> was modified. The start time, or both the duration and end time of the existing appointment were missing.

With regards to a similar problem posted on this link https://www.experts-exchange.com/questions/21816849/Calendar-Appointment-Problems.html#discussion , that was a syncing problem between Outlook and ACTS.