Error mounting lockproto lock_dlm

Hi,

I had a 2-nodes cluster running too fine under Ubuntu server 11.10, with 
cman, corosync, GFS2, OCFS2, clvm, ctdb, samba, winbind.

So I decided to upgrade :)

Under Precise (12.04), my OCFS2 partition is still working well.
CLVM is still OK, nicely speaking with the dlm layer (dlm_controld).

I ran "dlm_controld -D" and I can see the nice interaction with clvmd 
when ran.

But when I try to mount any GFS2 partition (either directly with 
mount.gfs2, or via the init.d script), I get the good old error:

| gfs_controld join connect error: Connection refused
| error mounting lockproto lock_dlm

When getting this, I don't see the smallest contact with dlm_controld 
(ran with -D, it should blink somewhere).

I guess something has changed : in Precise, here are the version numbers :
- libdlm3        3.1.7
- libdlmcontrol3 3.1.7
- gfs2-utils     3.1.3

What point must I check to explain to mount.gfs2 that dlm is actually up 
and running?
Does all that depend on other components I should check?