Disappearing inbox

We have IMAP turned on and our mail client is Windows Mail on Vista. All of the Zoho folders show up in the client except the inbox. When I right click on the Zoho folder, then select IMAP folders, the inbox is in the list. I can "Go To" the inbox and it will be visible until the next mail refresh or until I close & re-open the mail client. The inbox folder then disappears again and I have to repeat the process to get it to reappear.

Que Pasa?

Thanks.