when adding 2nd node in clusterXL , cluster stops passing traffic

[chgoIT]

I have 2 NGX R61 nodes just upgraded from v.R60. All custer configuration was re-imported in clusterXL after migration, so no changes in rules were made. When only one node in the cluster, traffic is passing fine, but as soon as the second node is added, both go in "ready" state, and none passing traffic. Sniffer on the nodes show activity on synch interfaces only. We tried destroyig and re-building the cluster, cleaninig installation on nodes and reinstalling, re-joining the cluster, both from XL and nodes interfaces and nothing helps. 2 tickets down the road with Checkpoint, still no luck. Also tried switching cluster mode from HA new mode to LB, both multicast and unicast, no luck. It's almost as though nodes are cluster-unaware , even though they pass packets on the synch.
Any help or ideas will be greatly appreciated. Thanks!