I have seen this type of behavior before. For me, I had my data lif set to accept the wrong protocol (I was using the iSCSI driver, but my lif only allowed nfs). Unfortunately, an unsuccessful attach doesn't usually leave any user-facing traces, other than the volume still being in "available" state, and nova not showing the attachment. You should check the cinder volume and nova logs for errors during the attach process to try and figure out what has gone wrong.
2014-05-27 13:51:34.342 27773 TRACE nova.virt.block_device [instance: 5273a931-b10f-4465-9bdb-b0a3893bd1a6] Stderr: 'mount: wrong fs type, bad option, bad superblock on 10.238.229.43:/open_cinder,\n missing codepage or helper program, or other error\n (for several filesystems (e.g. nfs, cifs) you might\n need a /sbin/mount.<type> helper program)\n In some cases useful info is found in syslog - try\n dmesg | tail or so\n\n'