Rebalance fails with error from ns_single_vbucket_mover:mover/6

The failure happens with the test on a 7 node cluster (http://qa.hq.northscale.net/job/centos-64-2.0-swap-rebalance/71/):
./testrunner -i /tmp/swaprebalance.ini -t swaprebalance.SwapRebalanceBasicTests.do_test,replica=2,num-buckets=1,num-swap=1

Below error can be seen in the diagnostics:

[rebalance:error] [2012-07-16 6:58:18] [ns_1@10.3.121.92:<0.11606.20>:ns_vbucket_mover:handle_info:176] <0.16459.20> exited with {badmatch,[{<0.16460.20>,
{badmatch,[

{<19236.1787.9>,normal}]}}]}
[ns_server:info] [2012-07-16 6:58:18] [ns_1@10.3.121.92:<0.16591.20>:ns_single_vbucket_mover:mover_inner:88] Got exit message (parent is <0.11606.20>). Exiting...
{'EXIT',<0.11606.20>,
{badmatch,[{<0.16460.20>,{badmatch,[{<19236.1787.9>,normal}

]}}]}}

[error_logger:error] [2012-07-16 6:58:18] [ns_1@10.3.121.92:error_logger:ale_error_logger_handler:log_report:72]
=========================CRASH REPORT=========================
crasher:
initial call: ns_single_vbucket_mover:mover/6
pid: <0.16591.20>
registered_name: []
exception exit: {exited,
{'EXIT',<0.11606.20>,
{badmatch,
[{<0.16460.20>,
{badmatch,[

{<19236.1787.9>,normal}]}}]}}}
in function ns_single_vbucket_mover:mover_inner/6
in call from ns_replicas_builder:try_with_maybe_ignorant_after/2
in call from ns_single_vbucket_mover:mover/6
ancestors: [<0.11606.20>,<0.11546.20>]
messages: [{'EXIT',<0.11606.20>,
{badmatch,
[{<0.16460.20>,
{badmatch,[{<19236.1787.9>,normal}

]}}]}}]
links: [<0.11606.20>,<0.16593.20>]
dictionary: [

{cleanup_list,[<0.16592.20>]}

]
trap_exit: true
status: running
heap_size: 987
stack_size: 24
reductions: 1761
neighbours:

Diagnostics are attached.