Yes, IMAP in Outlook 2010 on my company's server.
Strangely, Outlook has been updating all server folders with the exception of only one (maybe because that one was created in AM?).
The solution is as follows:
(a) open Folders tab in Outlook
(b) press IMAP Folders button and the dialog will open
(c) enter a folder's name in the search line and press Query
(d) when a folder appears in the list press Subscribe and Apply - now it's on the Outlook's folder list!
Looks like the problem is either with Outlook or our server's configuration...
Anyway, Paris Geek, thanks for your clues!