Outlook Express has a problem with the way Courier IMAP arranges users' mail folders, i.e., how it names them to distinguish between public and private folders. The most obvious effect of this is that Outlook Express seems unable to create any "top level" folders, only subfolders of "Inbox". I don't know if your problem is related to this, but there's one way to find out.

When configuring the settings for an IMAP-based account in OE, there's an option under the "IMAP" tab called "Root folder path". Set this to "INBOX." (without the quotes, with the period, with all-caps). That will clear up the sub-folders problem, and may clear up the other quirks as well.

The FAQ gives more info about this at: http://www.inter7.com/courierimap/FAQ.html#namespace

Hope this helps!