I am having the same issue. Research has provided no suitable solution, although I have recently noticed that "Outlook 2002" is not listed in the compatible software for IOS4. I updated to iTunes 10.5.2 hoping that a solution would be included, but to no avail. Everything was working fine until I updated to iTunes 10.5. I am very disapointed.
Could anyone provide a link to possible roll back my iTunes to a prior version??
I had the same problem but have just solved it.
My new iPhone 4s wouldn't transfer calendar entries to Outlook 2007. Although any entries input to Outlook transferred to the phone.
Reseting the sync history has worked. So now appointments that I input to the phone update outlook.
I hope this helps. Here is the link for the detail: http://support.apple.com/kb/HT1692
UPDATE: My problem was not related to the Sync History, rather the fact the Apple decided to stop supporting Outlook versions older than 2003. I realize that I shouldn't rely on software thats almost 10 years old, but I figured, if it ain't broke, don't fix it. I resolved my calendar sync issues by upgrading to a newer version of Outlook.
Before resorting to this, I successfuly rolled back my iTunes to an earlier version (following directions easily found via Google), but the older version of iTunes didn't recognize my "itunes_library.itl" file - in my iTunes folder. Older versions of this file are archived, so subbing one of those into the main iTunes directory solved that problem, however, I lost about a month of changes to my library. After tooling around with these issues, I finally decided that upgrading Outlook was a simpler solution.
It is curious, however, that iTunes didn't identiy my problem for me, maybe with a messge like "iTunes no longer supports sync for your version of Outlook". It is also curious that my probnlem was only for my calendar: my contacts and notes were still syncing fine both to and from the phone and computer.
Hope this helps others who experienced problems with iTunes and older verisons of Outlook.
I tried the same thing. Added Google account to phone, synced and my calendar was wiped completely from my iPhone. Keep restoring to an earlier back up to get those calendar entries but I get them for just about 5 minutes and then they are wiped away as soon as ActiveSync works. I use OUTLOOK 2010 and OFFICE 365.