moxi assertion on unexpected extlen

During weekend testing, especially around memcapable, I saw this crash report in osx console...

Process: moxi-debug [33229]
Path: /Users/steveyen/work/northscale/dev/wallace_master/components/tmp/repo_moxi/moxi/moxi-debug
Identifier: moxi-debug
Version: ??? (???)
Code Type: X86-64 (Native)
Parent Process: beam.smp [33209]

Date/Time: 2010-07-18 15:37:16.036 -0700
OS Version: Mac OS X 10.6.3 (10D578)
Report Version: 6

Exception Type: EXC_CRASH (SIGABRT)
Exception Codes: 0x0000000000000000, 0x0000000000000000
Crashed Thread: 1

Application Specific Information:
Assertion failed: (extlen == sizeof(response_get->message.body)), function cproxy_process_a2b_downstream_nread, file cproxy_protocol_a2b.c, line 539.

Thread 0: Dispatch queue: com.apple.main-thread
0 libSystem.B.dylib 0x00007fff841bc4ea kevent + 10
1 libevent-1.4.2.dylib 0x0000000100111213 kq_dispatch + 83
2 libevent-1.4.2.dylib 0x0000000100104d28 event_base_loop + 440
3 moxi 0x0000000100017fe2 main + 7022
4 moxi 0x0000000100001594 start + 52

Thread 1 Crashed:
0 libSystem.B.dylib 0x00007fff8421601e __semwait_signal_nocancel + 10
1 libSystem.B.dylib 0x00007fff84215f20 nanosleep$NOCANCEL + 129
2 libSystem.B.dylib 0x00007fff84272902 usleep$NOCANCEL + 57
3 libSystem.B.dylib 0x00007fff84291eb8 abort + 93
4 libSystem.B.dylib 0x00007fff8427eef0 __pthread_markcancel + 0
5 moxi 0x000000010003cf7d cproxy_process_a2b_downstream_nread + 1927
6 moxi 0x00000001000452fd cproxy_process_downstream_binary_nread + 312
7 moxi 0x00000001000099ec complete_nread + 458
8 moxi 0x0000000100013757 drive_machine + 2335
9 moxi 0x0000000100014bb6 event_handler + 285
10 libevent-1.4.2.dylib 0x0000000100105031 event_base_loop + 1217
11 moxi 0x00000001000202c9 worker_libevent + 274
12 libSystem.B.dylib 0x00007fff841dc8b6 _pthread_start + 331
13 libSystem.B.dylib 0x00007fff841dc769 thread_start + 13