If the root filesystem is compiled as a module, and not loaded on the failover node then failover hangs. Pretty obvious realy.
(cfs_root_failover calls do_kern_mount which calls get_fs_type which is forced to call request_module - result hang).
However there is nothing to force the loading of the root filesystem driver on the failover node.
A simple hack is to add it to the modules loaded by the ramdisk.
A cleaner way would to be to load it in cfs_setroot, or rather in the ssi kernel function called by cfs_setroot.