In short:

1.Create a replica set with 6 nodes ( 1 primary, 3 secondaries and 2 arbiters.)
2. Insert a lot of trivial documents.
3. While doing the insert run replSetReconfig repeatedly.

Expected outcome:
No issues.

Actual Outcome:
1.6.x: One secondary and one arbiter crash with the following backtrace:

Tue Mar 8 13:05:08 [initandlisten] connection accepted from 127.0.0.1:50215 #6
Tue Mar 8 13:05:08 Got signal: 11 (Segmentation fault).

Tue Mar 8 13:05:08 Backtrace:
0x824629 0x7f47172a41f0 0x66c10b 0x67020a 0x6682e2 0x797117 0x798538 0x5fb7e5 0x60029f 0x7074ba 0x70aaf6 0x82691b 0x83a4b0 0x7f4717d7e914 0x7f47173437dd
/home/behackett/mongo/bin/mongod(_ZN5mongo10abruptQuitEi+0x399) [0x824629]
/lib/libc.so.6(+0x321f0) [0x7f47172a41f0]
/home/behackett/mongo/bin/mongod(ZN5mongo11ReplSetImpl17_fillIsMasterHostEPKNS_6MemberERSt6vectorISsSaISsEES7_S7+0x2b) [0x66c10b]
/home/behackett/mongo/bin/mongod(_ZN5mongo11ReplSetImpl13_fillIsMasterERNS_14BSONObjBuilderE+0x27a) [0x67020a]
/home/behackett/mongo/bin/mongod(_ZN5mongo11CmdIsMaster3runERKSsRNS_7BSONObjERSsRNS_14BSONObjBuilderEb+0x52) [0x6682e2]
/home/behackett/mongo/bin/mongod(_ZN5mongo11execCommandEPNS_7CommandERNS_6ClientEiPKcRNS_7BSONObjERNS_14BSONObjBuilderEb+0x597) [0x797117]
/home/behackett/mongo/bin/mongod(_ZN5mongo12_runCommandsEPKcRNS_7BSONObjERNS_10BufBuilderERNS_14BSONObjBuilderEbi+0x798) [0x798538]
/home/behackett/mongo/bin/mongod(_ZN5mongo11runCommandsEPKcRNS_7BSONObjERNS_5CurOpERNS_10BufBuilderERNS_14BSONObjBuilderEbi+0x35) [0x5fb7e5]
/home/behackett/mongo/bin/mongod(ZN5mongo8runQueryERNS_7MessageERNS_12QueryMessageERNS_5CurOpES1+0x1bbf) [0x60029f]
/home/behackett/mongo/bin/mongod() [0x7074ba]
/home/behackett/mongo/bin/mongod(_ZN5mongo16assembleResponseERNS_7MessageERNS_10DbResponseERKNS_8SockAddrE+0x14d6) [0x70aaf6]
/home/behackett/mongo/bin/mongod(_ZN5mongo10connThreadEPNS_13MessagingPortE+0x30b) [0x82691b]
/home/behackett/mongo/bin/mongod(thread_proxy+0x80) [0x83a4b0]
/lib/libpthread.so.0(+0x6914) [0x7f4717d7e914]
/lib/libc.so.6(clone+0x6d) [0x7f47173437dd]

Tue Mar 8 13:05:08 dbexit:

1.8.0-rc1: Backtrace in the log of one secondary:

Tue Mar 8 13:19:46 [initandlisten] connection accepted from 127.0.0.1:43559 #9
Tue Mar 8 13:19:57 [replica set sync] DBClientCursor::init call() failed
Tue Mar 8 13:19:57 [replica set sync] Assertion failure r.haveCursor() db/repl/rs_sync.cpp 288
0x530b21 0x541131 0x69ffe6 0x6a0c00 0x6a10b1 0x7f41d9fb2c57 0x7f41da6db914 0x7f41d8d127dd
mongod(_ZN5mongo12sayDbContextEPKc+0xb1) [0x530b21]
mongod(_ZN5mongo8assertedEPKcS1_j+0xc1) [0x541131]
mongod(_ZN5mongo11ReplSetImpl8syncTailEv+0xd96) [0x69ffe6]
mongod(_ZN5mongo11ReplSetImpl10syncThreadEv+0x80) [0x6a0c00]
mongod(_ZN5mongo15startSyncThreadEv+0x1d1) [0x6a10b1]
/usr/lib/libboost_thread-mt-1_42.so.1.42.0(thread_proxy+0x77) [0x7f41d9fb2c57]
/lib/libpthread.so.0(+0x6914) [0x7f41da6db914]
/lib/libc.so.6(clone+0x6d) [0x7f41d8d127dd]
Tue Mar 8 13:19:57 [replica set sync] replSet syncThread: 0 assertion db/repl/rs_sync.cpp:288
Tue Mar 8 13:19:57 [conn9] end connection 127.0.0.1:43559