This is happening to me on regular basis, therefore I have submitted a bug:
http://bugs.kde.org/show_bug.cgi?id=121698

I am suprised that nobody else seems to have similar problem...

Regards,
Luka

On Wednesday 01 February 2006 07:23, Luka Renko wrote:
> Update: I had to remove my Disconnected IMAP account and add it again in
> order to get read-write Inbox. Strange.
>
> Regards,
> Luka
>
> On Monday 30 January 2006 08:09, Luka Renko wrote:
> > Hello,
> >
> > I am using KMail 1.9.1 (Kubuntu 5.10, KDE 3.5, always used through
> > Kontact) to
> > access my mailbox on Exchange 2003 server over IMAP. I use disconnected
> > IMAP
> >
> > in order to have offline access to my mailbox.
> >
> > In my mailbox, I have several folders (including non-email ones, like
> > Contacts, Tasks...), but I have only subscribed to the ones I need
> > (personal
> >
> > mail folders).
> >
> > There are two annoying things:
> >
> > 1. Sometimes after restart of Kontact I get warnings for several (but not
> > all)
> > folders on Exchange IMAP that Kmail is unable to *create* folder on IMAP
> > server. I just confirm warning messages and it looks like that everything
> > works as expected afterwards, besides if this is related to my second
> > problem.
> >
> > 2. Inbox folder on IMAP server becomes read-only
> > Sometimes after the start Kmail claims that my Inbox (and only this
> > folder!)
> >
> > is read-only. I cannot do any delete/move/copy to operation. I have
> > checked options and have not find a way to control read-only/read-write
> > mode of folders. Funny things, after several restarts, playing with IMAP
> > troubleshooting (rebuild...) options and so on, the folder becomes
> > read-write
> > again?!?
> >
> >
> > Anybody else experiencing such weird problems with KMail?
> >
> > Regards,
> > Luka