I get these errors when running the l2switch distribution and starting mininet.

2014-07-25 18:47:38.625 EDT [md-sal-binding-notification-0] ERROR o.o.c.sal.binding.impl.NotifyTask - Unhandled exception thrown by listener: org.opendaylight.l2switch.addressobserver.AddressObserver$$Broker$ListenerInvoker@5248e0b1
java.lang.UnsupportedOperationException: null
at java.util.AbstractMap.put(AbstractMap.java:203) ~[na:1.7.0_25]
at org.opendaylight.yang.gen.v1.urn.opendaylight.inventory.rev130819.node.NodeConnectorBuilder.addAugmentation(NodeConnectorBuilder.java:108) ~[na:na]
at org.opendaylight.l2switch.addressobserver.AddressObservationWriter.addAddress(AddressObservationWriter.java:133) ~[na:na]
at org.opendaylight.l2switch.addressobserver.AddressObserver.onIpv6PacketReceived(AddressObserver.java:144) ~[na:na]
at org.opendaylight.l2switch.addressobserver.AddressObserver$$Broker$ListenerInvoker.onNotification(AddressObserver$$Broker$ListenerInvoker.java) ~[na:na]
at org.opendaylight.controller.sal.binding.impl.AbstractNotificationListenerRegistration.notify(AbstractNotificationListenerRegistration.java:38) ~[na:na]

We think this may be the root cause of this error in mdhosttracker:

2014-07-25 19:37:28.583 EDT [pool-9-thread-1] WARN o.o.c.m.s.d.s.i.InMemoryDOMDataStore - Store Tx: DOM-OPER-44 Data Precondition failed for (urn:opendaylight:mdhosttracker?revision=2014-06-24)hosts.
org.opendaylight.yangtools.yang.data.api.schema.tree.ModifiedNodeDoesNotExistException: Node does not exist. Could not modify its children.