Kmail is not working with my Cyrus Imap server

Hi there,

Kontact is a nice program, and I'd like to use it for my email, 
calendar, etc. I have a Cyrus Imap server (Cyrus Imap 2.2 on Debian 4). 
Cyrus imap runs fine, and I can access it from Thunderbird, Evolution, 
and from Outlook.

Only with Kontact/Kmail (4:3.5.10-0ubuntu1~hardy3), I can't access my 
mail. Apparently, Kmail does not fetch the folder list from the server. 
I can't find any error message. Kmail is just hanging here and not doing 
anything when I click on the folder icon.

Does anyone have experience with this issue? Is there any way to tell 
what Kmail is trying to do, or to get an error message?

Thanks for your help in advance,
Gordon