rebalance crashed under load with 5 buckets

1.6.0beta4-84
centos 5.4 32 bit
2 nodes

1) start up 1 node and create default bucket
2) create 2 membase buckets
3) create 2 memcached buckets
4) load a small amount of data into each node
5) run memslap against default bucket, against the first node
6) add a second node
7) rebalance

About halfway through the rebalance, rebalance exited.

Using vbucketctl I saw that the memcached buckets didn't have proper active vbuckets

memcached1
node1: 1 active
node2: 1 active

memcached2
node1: 815 active
node2: 209 active