iphone calendar will not pull any info from Exchange 2003 through active sync

I have one user's iphone which all of a sudden will no longer sync information from the users exchange account.  The mail and contacts work fine and sync normally.  No calendar information will pull down to the phone.  If i put in an event in the calendar on the iphone, the event will show up in the users outlook calendar.  But putting in events in the calendar will not flow to the phone and pre existing items in the outlook calendar will not sync with the phone.

It's not the phone as I have tried to set up the exchange account on another phone.  Same deal - Mail and contacts work fine but Calendar will not sync.  Also, Outlook Web access works fine for the user and after logging into owa, all calendar events can be seen.  I have checked every setting on the iphone for syncing the info with Exchange Active sync.  Not sure where to go from here.
Who is Participating?

[Product update] Infrastructure Analysis Tool is now available with Business Accounts.Learn More

I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

There may be some entries in the calendar that it's having issues with.  I had this happen for an iphone user before and the only solution I found was to delete all of her calendar entries that were older than about 30 days.
Clarification:  I had to delete the calendar entries within the user's mailbox and then re-enable the calendar synching on the iPhone.

You can also experiment by copying the calendar and giving it a different name, then re-enabling the calendar sync and gradually adding in calendar entries from the old one to the new blank one to see at what point the phone stops synching.
Alan HardistyCo-OwnerCommented:
Please check your configuration against my Exchange 2003 / Activesync article, run the tests and if everything passes, let me know:
If everything passes happily, please check the following registry setting and if not present, add it and then restart the server:
DWORD - ProActiveScanning=1

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
Another thing to check:  make sure there are no custom forms configured in the user's Outlook.  Sometimes certain add-in programs will install custom forms and make it so that whenever you create a new calendar event in OUtlook, it is created using one of those forms.  This is fine as long as you're still using Outlook to manage the calendar.

Unfortunately the iPhone (and most mobile devices) almost always cannot read these forms, and fail to sync over these events as a result.
ccmadminsAuthor Commented:
Ultimately it ended up being a permissions problem on the server that should not have been changed but was somehow.  It had to do with forms based authentication.  We also had the clear the forms cache in the User's outlook file to get it to work.  
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
Email Protocols

From novice to tech pro — start learning today.