Exchange OWA Unable to Access Some Calendar Items - Outlook Works OK

I have an interesting seemingly widespread problem with OWA on Exchange 2003.  I have users reporting that some calendar items that were entered using Outlook are not syncing with their mobile device.  

While troubleshooting I found that accessing their mailbox from OWA I was able to see the missing calendar item on the calendar but was unable to open it.  Attempting to open it reports HTTP 500 Internal Server Error - The website cannot display the page.  However, I CAN open the same item in Outlook.  

There are many items in the calendar and only a few are not accessible from OWA.  I am unable to recreate the problem.  The person that enters the calendar items insists that all calendar items are created using the exact same process and all are basically the same structure, i.e. the format of the subject line is basically the same with the same special characters present in all calendar items.  I thought at first the subject line in the offending items was too long and contained unusual special characters such as : and / or \ but many with the same structure work fine.  

I did a side-by-side comparison of the URLS from one good and one bad calendar item and nothing seems to be obviously wrong.

I have opened the bad calendar items with mdbvu32 to see if there was something strange but so far I have only noticed that mdbvu32 crashes a lot.  I did receive the following message when using mdbvu32:

The permission on Mapi_folder - Calendar are incorrectly ordered which may cause some entries to be ineffective.  Press OK to continue and sort the permissions correctly or cancel to reset the permissions.  

Choosing OK shows the delegate permissions on the folder.  Clicking OK on the permissions dialogue reports a message about Deny permissions being assigned and they will override other access permissions, just normal ACL stuff.

Another error I received when opening the calendar item properties was:

CPropDlg::RedrawPropTable() IpEntry->GetProps(): MAPI_W_ERRORS_RETURNED

The only problem is, I received this error when opening bad calendar items AND when opening GOOD calendar items.  So I think these messages may be misleading even though I'm not sure what the errors mean.

My environment is as follows:

Windows Server 2003 SP2
Exchange 2003 SP2
Outlook 2007
OWA with Forms Authentication Enabled
Testing was performed using IE8 from a domain PC on internal network.  Accessing OWA externally exhibits the same errors.  

I'm at a loss.  Can anyone offer another approach to the problem that I haven't thought of?

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I don't really have an answer, but since no-one else is responding, I'd suggest you try an integrity check of the DB, in case there are some corrupted items.  You need to do it when things are quiet, though, because the DB needs to be offline.

Here's a description of the parameters to supply, but don't use the -fix one first time round.  You may need to think about how important the appointments are before you expose everything else to this sort of risk.
JDBTechAuthor Commented:
Thanks for the comment LeeDerbyshire.  About a month ago I took the database offline and ran an integrity check.  The database checks out clean.  :(

I'm not sure where to go from here.  I have to find out why some calendar items can't be opened with OWA (even though they show up on the proper day with the correct subject) before I can attempt to determine what caused the problem.  

Maybe there is someone that knows more than I do about the internal properties of an Exchange calendar item and could tell me which property OWA uses to access the item??  I thought it was just the subject line represented in a url like the following:


Is there a specific property on the calendar item that represents the URL?  I couldn't find it with mdbvu32 but there is a large list of properties.  I could have missed something important.
You have the correct URL, but it can be used in different ways.  Used in a GET request, you will get the OWA GUI display for the item.  Used in something like PROPFIND (as sent by a webdav app), you can use the URL to access properties.  It's also possible that the data is okay in the store, but the access method (OWA in this case) is upset by some aspect of it (a confusing recurrence pattern, say).  You might try something like Outlook Spy as yet another way of inspecting the values that Outlook sees.  It will show errors for individual properties if any are returned.

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JDBTechAuthor Commented:
I'll take a look at the offending calendar item with outlookspy and see if anything shows up.  Opening the item from Outlook 2007 works fine and it never reports anything weird but maybe I can see something mdbvu32 didn't see.  I'll report back asap.  Thanks again!
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