Running SLES 11 SP2 with latest patches (as of 15/7/2013), SLES HAE SP2 OCFS2 Version 1.6_3.0.13, XEN
5 Node Cluster OCFS2 gets broken by the latest kernel update.

All other SLES nodes running kernel 3.0.58
Updated one server to kernel 3.0.80 and ocfs2 will no longer mount

ocfs2 Internal logic failure while trying to join the group
Jul 15 12:48:44 sl-bne-hs23-01 kernel: [ 3496.524201] (mount.ocfs2,21615,11):o2hb_map_slot_data:1638 ERROR: status = -12
Jul 15 12:48:44 sl-bne-hs23-01 kernel: [ 3496.524208] (mount.ocfs2,21615,11):o2hb_region_dev_write:1768 ERROR: status = -12
By back rev'ing the kernel to 3.0.58, the system starts up again with no problems, ocfs2 mounts coming up correctly
Version 3.0.74 was not tested due to the need to get a live system back on line. No other patches had to be downgraded on the 5th server. Just the kernel-xen and the kernel-xen-base

This kernel version has been marked protected on our SLES cluster servers until a resolution is found.