I have been banging my head on the desk for about a week with this, searching every database I can find without solution.
About 6 months ago (give or take) we started receiving this error "This item cannot be displayed in the Reading Pane. Open the item to read its contents.", and it only happens sometimes, no specific message, and "sometimes" if you double click on the message, it will open, or it will say "Can't open item. Operation failed.".
Details on setup:
Windows 2003 Server (SP2), Microsoft Exchange Server 2003 (SP2), clients using Outlook 2003 and one using 2007. Error occurs across all clients (haven't tested OWA much, but haven't seen it on OWA yet, doesn't mean its not happening, just means it hasn't happened to me yet).
So far, I've tried running ISINTEG -s (server) -fix -test alltests on both mailbox db and public folder db, also ran ESEUTIL /G (pub and mailbox db's). I've actually done this twice with no good result. I've tried MANY different machines, including our terminal server, I've tried creating new outlook profiles, different windows profiles, all on different machines, even latest version of Outlook 2007 and they all eventually produce the error. I've changed the mailbox settings to download all messages, not just some, no effect.
I have also changed the diagnostic logging in Exchange and the only thing I see that looks like it could be causing the problem is:
Error: Unexpected error 0x8004010f occurred in "EcVirusScanOneMessage".
I have researched this and the most I can find is people saying to run ESEUTIL and ISINTEG, which I've already done twice and it hasn't fixed it. This could be completely unrelated from my main problem, but if I can fix that, it gets rid of one possible problem.
Any help would be very much apperciated. As I said, this error doesn't happen on any specific type of message or any persons specific mailbox, its pretty much across the server and one second you click a message and it might open, the next, you get the error and sometimes it only happens for a second, others it might not let you open any messages, or some but not others. It's been very strange and hard to trace.
Thanks for reading this long description. I've done a lot of work on this so far and I'd hate to waste someones time by not including what I've already done.