dovecot - Mar 2012 - INBOX cant be created

Inbox does not exists on disk, but following command sequence will not 
create it.

2 select INBOX
2 NO Mailbox doesn't exist: INBOX
3 create INBOX
3 NO [ALREADYEXISTS] Mailbox already exists: INBOX

i think its bug

doveadm does not works too:

sudo doveadm mailbox create -u admin INBOX
doveadm(admin): Error: Can't create mailbox INBOX: Permission denied
sudo doveadm mailbox create -u admin INBOX.2
(works)