Strange IMAP behaviour

Hello,

I have the following problem using Windows Mail (French) on Windows Vista
(Ultimate) with several IMAP accounts :

Among these accounts, I have one account that doesn't display the "INBOX"
(actually named "Boîte de réception"), BUT it properly displays all OTHER
folders on the same account.

This account is the only account having this problem. All other accounts
have their "INBOX" folder displayed properly.

If I open the IMAP folder dialog, I can see that the folder is actually
present, but it appears like if it was a "hidden" folder.
As it is the "INBOX" folder, I cannot make it visible because the "Display"
(actually "Afficher" in French) button is disabled.

I can go in the folder and read mail from this dialog using the "Atteindre"
("Reach"?) button. This makes the folder visible, but only until the end of
the session. If I close Windows Mail and start it again, the same problem
comes back.

Reinitializing the folder list doesn't fix the problem : the "INBOX" folder
is rebuilt hidden again.

Deleting the account and recreating it doesn't fix the problem either : same
result as above.

Going inside the "C:\Users\[user]\AppData\Local\Microsoft\Windows Mail"
folder and deleting there the folder having the account name doesn't fix the
problem either : same result as above.

====> The same account works perfectly well using Outlook Express on a
Windows XP computer!

Any idea?

Gingko