If during migrating Cluster volumes from one cluster to another or if a cluster was taken down incorrectly. Those volumes would not be able to join the new cluster due to the persistent reservation flag set by cluster service. Easy way to make sure to clear the flag before migrating this volume to a new cluster is remove it from the old cluster storage first. The command below will remove the reservation.
cluster.exe node %nodename% /clear:disknumber
References:
http://technet.microsoft.com/en-us/library/cc732694(WS.10).aspx