Problem connecting to CVS with SSH

I have a problem using Anthill on a CVS repository with SSH  
authentication.
So: I have set my Anthill project (coopn) to use the following CVSROOT:

    :ext:[email protected]:/usr/local/cvsroot

I have also set the CVS_RSH environment variable for the user me to  
be "ssh".
Also, I have done manually a cvs checkout once to be sure that the  
RSA key was added to the known_hosts file. In fact, the server  
holding the CVS repository and the server running Anthill are the  
same server, smv.unige.ch.

When I try to build my project, it fails immediately. The weird thing  
is, if I keep a console open (with user me logged in) when clicking  
"Build", I get the request for authorizing the connecting server:

    The authenticity of host 'smv.unige.ch (129.194.69.14)' can't be  
established.
    RSA key fingerprint is 0f:08:dc:c6:95:50:fc:c1:06:52:0f: 
5e:df:b2:c4:0d.
    Are you sure you want to continue connecting (yes/no)?

although as I said this server is already in the known_hosts file (I  
have checked the fingerprint, it's the same I got when doing it  
manually).
If I answer "yes", the console starts printing infinite lines with  
the "y" character until I press ctrl-c (but the build had already  
failed before answering).

The catalina.out file, at the point of executing CVS, states:

    Executing: cvs -d :ext:[email protected]:/usr/local/cvsroot  
checkout -A coopn
    smv.unige.ch: Connection refused

Needless to say, if I run that same command manually it works (and  
does not ask for RSA authentication).
Still, one detail is not clear to me, although I'm not sure it's  
related: how is Anthill supposed to provide the ssh password for  
connection?!?

If anybody has an idea, that would be of great help.
Thanks,
Matteo