Microsoft has a fix for that problem:
http://support.microsoft.com/kb/941090
Although it only mentions 'Outbox', the fix works for all folders.
--
Gary VanderMolen, MS-MVP (WLMail)
"Karen Alvarez" <(E-Mail Removed)> wrote in message
news:7075A0E4-8E6D-417C-B98C-(E-Mail Removed)...
>I get an error message reading
> "Message could not be displayed
> Windows Mail encountered an unexpected problem while displaying this
> message. Check your computer for low memory or low disk space and try again".
>
> I have lots of disk space, but can't delete these messages and I think
> they're causing a conflict because I can't send messages from that email
> address and have to use another one I have.
>
> Does someone out there know what I can do? I had this problem several
> months ago and suddenly it fixed itself when I clicked on "local folders"
> above the "inbox", but it's not working now.
>