Rebalance failes because of memcached request timeout

Setup [cluster : 10.1.3.74 to 0.1.3.80]

1. Setup a 7 node cluster [74, 75, 76, 77, 78,79 ,80]
2. Failovered nodes [75, 77, 78] - successful failovers for all
3. Rebalance cluster [ejected Nodes - 75,77,78 cluster - 74, 75, 76, 77, 78, 79, 80]

Output
Rebalance Failed as
[2012-05-24 07:04:43,473] - [rest_client:749] ERROR -

{u'status': u'none', u'errorMessage': u'Rebalance failed. See logs for detailed reason. You can try rebalance again.'}

- rebalance failed
ERROR]

This is an automated test-_add_back_failed_node on Swap RebalanceTests.
http://qa.hq.northscale.net/view/1.8.1/job/181-centos-64-swaprebalance-tests/lastBuild/testReport/junit/swaprebalance/SwapRebalanceFailedTests/swaprebalance_SwapRebalanceFailedTests_test_add_back_failed_node_get_logs_True_replica_1_num_swap_3_num_nodes_7_num_buckets_1_spec_py_swaprebalance/

Error from the ns_server log
[error_logger:error] [2012-05-24 13:09:15] [ns_1@10.1.3.79:error_logger:ale_error_logger_handler:log_report:72]
=========================CRASH REPORT=========================
crasher:
initial call: ebucketmigrator_srv:init/1
pid: <0.884.0>
registered_name: []
exception exit: downstream_closed
in function gen_server:terminate/6
ancestors: ['ns_vbm_sup-default','single_bucket_sup-default',<0.775.0>]
messages: [

{'EXIT',<0.891.0>,killed}

]
links: [<0.786.0>,<0.57.0>]
dictionary: []
trap_exit: true
status: running
heap_size: 2584
stack_size: 24
reductions: 13663
neighbours:

Attaching the ns_server logs at https://s3.amazonaws.com/bugdb/jira/swap_check/swap_01.tar