Murder / frontend does not connect to backend

[arnaud at opensquad.com]

Hello,

I'm setting up a cyrus murder in a lab and I'm facing a problem.
The architecture is quite simple : 1 frontend, 1 backend and a mupdate master

We are using cyrus 2.2.13-10 on Debian etch.

The Mupdate seems OK, I can LIST from everywhere. If I create a mailbox on the
backend I can see it with mupdatetest on the frontend quickly.

But I cannot make a single IMAP SELECT command on the frontend.
This problem can be tracked  with cyradm.
When I try to create a mailbox. I've this strange message and there is NO trafic
between frontend and backend.  The same message arises when connecting with a
IMAP client
----
localhost> cm user.user1.tutu
createmailbox: Server(s) unavailable to complete operation

Log line associated :
Mar 23 00:01:31 proxy1 cyrus/proxyd[12155]: connect(default) failed: Invalid
argument
---
But if I try to delete a mailbox I can see trafic between front and back
servers.

So my (maybe first) question is :
Why there is no communication when connecting to IMAP ?
What does mean "connect(default) failed: Invalid argument" in the log
Everything I found was related to authentication but this does not seem an issue
in my setup.

Thanks in advance

--
  Arnaud Brugnon
  Opensquad