OWA encountered an unexpected error and was unable to handle your request when viewing messages with attachments

When using OWA to view messages with attachments we get the following error:

Outlook Web Access encountered an unexpected error and was unable to handle your request.

It doesn't appear to happen with all file types though. pdf, jpg, wav, ect work but doc, docx, xls, xlsx, ppt, ect don't. I have verified in Exchange management console --> Server configuration --> Client access --> owa (default web site) --> properties --> Public Computer file Access --> Customize that the file types are set to allow.

This appears to be affecting all users, all browser types, and all modes of OWA (public, private, light).

Here is the details from the clipboard of the error :

Url: https://mail.xyz.com:443/owa/forms/premium/ReadMessage.aspx?ae=Item&a=Preview&t=IPM.Note&id=RgAAAAC4jMrDVl8%2bQ5tzg9Zs5UhdBwAVd7RuslSxTb4gRrbskp6eAAACcP%2bsAAAVd7RuslSxTb4gRrbskp6eAAAFR0cuAAAJ
User host address:
User: xxx
EX Address: /o=Exchange/ou=First Administrative Group/cn=Recipients/cn=xxx
SMTP Address: xxx@xyz
OWA version:
Mailbox server: scdc-exchange-1.xyz.com

Exception type: System.IO.IOException
Exception message: Illegal operation attempted on a registry key that has been marked for deletion.

Call stack

Microsoft.Win32.RegistryKey.Win32Error(Int32 errorCode, String str)
Microsoft.Exchange.Clients.Owa.Core.AttachmentLevelLookup.GetAttachmentLevel(Attachment attachment, UserContext userContext)
Microsoft.Exchange.Clients.Owa.Core.Controls.AttachmentWellInfo..ctor(Attachment attachment, Boolean isJunkOrPhishing)
Microsoft.Exchange.Clients.Owa.Core.Controls.AttachmentUtility.GetAttachmentList(Item item, Boolean isLoggedOnFromPublicComputer, Boolean isEmbeddedItem, Boolean discardInline, Boolean forceEnableItemLink)
Microsoft.Exchange.Clients.Owa.Premium.Controls.AttachmentWell.GetAttachmentInformation(Item item, Boolean isLoggedOnFromPublicComputer, Boolean isEmbeddedItem, Boolean forceEnableItemLink)
ASP.forms_premium_readmessage_aspx.__Render__control1(HtmlTextWriter __w, Control parameterContainer)
System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children)
System.Web.UI.Page.Render(HtmlTextWriter writer)
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)

Thanks in advance for any help.

Who is Participating?
kevalaConnect With a Mentor Commented:
It's confusing, but, certain memory issues, and even threads being locked can cause this exact behavior.
We access different parts of the product (high level explaination there) to open certain file types. Example, for jpg, mp3, etc. we go here, for .doc, pdf, etc. we go there.
It's very possible that there was a really, really low level performance problem, or memory issue, or threads locked that was preventing those files from being accessed.

If you think about it, all IISReset would be doing that is related is freeing all related threads and memory blocks to be reallocated.
Are you able to save the attachment?

Also, what version(s) of I.E. have you tried? If multiple, does it happen with all versions?

I've also seen this with performance problems on the server. Not to alarm you with this but, are you getting any memory related warnings or errors in the Application logs in event viewer? (Specifically low PTEs)
Also, try accessing OWA directly on the Exchange server in IIS manager. Locate the default website, the right-click and choose browse on the Exchange directory. Login through here and try to view one.
w3isysadminAuthor Commented:

we weren't able to save the attachments. we couldn't even get the message to show up.

We tried from IE 6, IE 7, IE 8, google chrome, Mozilla 3 and all produced the same error.

I tried to access it from the server itself and that too failed.

There was nothing in the event logs in regards to memory issues that I found.

What we did try next though has fixed the problem. We did a IIS reset on the CAS server and it appears to have fixed the issue. I'm still not certain on what it could be or why it happened to begin with.

w3isysadminAuthor Commented:
I think what's even more of a mystery is why it was only certain file types that this would happend too. any message with no attachments worked fine. messages with pdf's, jpg, and wav files worked fine. It was just with zip, doc, docx, xls, xlsx, and ppt that we seen the issue.

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