[Dovecot] SSL failures on 1.0B3

I have setup Dovecot 1.0B3, and IMAP works fine, but I cannot get
IMAPS to work. I've generated the keys with the mkcert script and
Thunderbird can see and accept the certificate but tosses an error
just after that.

In my log, I'm getting: dovecot: Apr 03 19:07:43 Warning: imap-login: SSL_accept() failed:
error:140D308A:SSL routines:TLS1_SETUP_KEY_BLOCK:cipher or hash
unavailable [x.x.x.x] dovecot: Apr 03 19:07:43 Info: imap-login: Disconnected: rip=x.x.x.x,
lip=x.x.x.x, TLS

Can anyone give me a tip as to what is the matter? I don't understand
these ssl errors,

Thanks,

-- Joe