rebalance (vbucketmigrator) gets stuck at 98.8% done

In build 1.6.0beta3b-21 (where there's no more port_adaptor), rebalance gets stuck at 98.8% done, and there's a stuck vbucketmigrator -t process. See...

http://skitch.com/steveyen/d1uit/northscale-console-1.6.0beta3b-63-g55826ce

On the joinee node, the vbucketmigrator process has been there for several minutes now. Server nodes were rhel 64-bit...

[root@Config126VM0 ~]# ps -ef | grep vbu
100 4584 305 0 02:50 ? 00:00:00 ./bin/vbucketmigrator/vbucketmigrator -a default -h 10.1.4.11:11210 -d 10.1.4.12:11210 -v -t -T 10 -b 7
root 6264 6205 0 02:53 pts/3 00:00:00 grep vbu

[root@Config126VM0 ~]# pstack 4584
Thread 2 (Thread 1092995392 (LWP 4588)):
#0 0x00000037e4cc439b in read () from /lib64/libc.so.6
#1 0x00000037e4c6c797 in _IO_new_file_underflow () from /lib64/libc.so.6
#2 0x00000037e4c6d15e in _IO_default_uflow_internal () from /lib64/libc.so.6
#3 0x00000037e4c68a1b in getc () from /lib64/libc.so.6
#4 0x000000000040953c in check_stdin_thread ()
#5 0x00000037e5806307 in start_thread () from /lib64/libpthread.so.0
#6 0x00000037e4cd1ded in clone () from /lib64/libc.so.6
Thread 1 (Thread 47856627682976 (LWP 4584)):
#0 0x00000037e4cd21d8 in epoll_wait () from /lib64/libc.so.6
#1 0x0000000000411300 in epoll_dispatch ()
#2 0x000000000040f831 in event_base_loop ()
#3 0x000000000040b1db in main ()
#0 0x00000037e4cd21d8 in epoll_wait () from /lib64/libc.so.6