We run two replica sets, three nodes in each set (mongo v2.4.5)
Our primary server in one of the replicas crashed with the following message:

Wed Nov  6 20:40:30.380 [repl writer worker 6] ERROR: writer worker caught exception: E11000 duplicate key error index: markover.reply.$pollID_1_replyID_1  dup key: { : null, : null } on: { ts: Timestamp 1383770430000|8, h: 4197632611217932450, v: 2, op: "u", ns: "markover.reply", o2:

{ _id: ObjectId('51eebff86ea332056f00034b') }

, o: { $set:

{ uncertain: false, vote: "testvote" }

} }
Wed Nov  6 20:40:30.380 [repl writer worker 6]   Fatal Assertion 16360
0xdd9e31 0xd99e63 0xc2342c 0xda7971 0xe225d9 0x7f06c79c7c6b 0x7f06c6d6d5ed
 /usr/bin/mongod(_ZN5mongo15printStackTraceERSo+0x21) [0xdd9e31]
 /usr/bin/mongod(_ZN5mongo13fassertFailedEi+0xa3) [0xd99e63]
 /usr/bin/mongod(_ZN5mongo7replset14multiSyncApplyERKSt6vectorINS_7BSONObjESaIS2_EEPNS0_8SyncTailE+0x12c) [0xc2342c]
 /usr/bin/mongod(_ZN5mongo10threadpool6Worker4loopEv+0x281) [0xda7971]
 /usr/bin/mongod() [0xe225d9]
 /lib64/libpthread.so.0(+0x7c6b) [0x7f06c79c7c6b]
 /lib64/libc.so.6(clone+0x6d) [0x7f06c6d6d5ed]
Wed Nov  6 20:40:30.427 [repl writer worker 6]

***aborting after fassert() failure

Wed Nov  6 20:40:30.427 Got signal: 6 (Aborted).

Wed Nov  6 20:40:30.438 Backtrace:
0xdd9e31 0x6d0d09 0x7f06c6cbf9c0 0x7f06c6cbf945 0x7f06c6cc125b 0xd99e9e 0xc2342c 0xda7971 0xe225d9 0x7f06c79c7c6b 0x7f06c6d6d5ed
 /usr/bin/mongod(_ZN5mongo15printStackTraceERSo+0x21) [0xdd9e31]
 /usr/bin/mongod(_ZN5mongo10abruptQuitEi+0x399) [0x6d0d09]
 /lib64/libc.so.6(+0x349c0) [0x7f06c6cbf9c0]
 /lib64/libc.so.6(gsignal+0x35) [0x7f06c6cbf945]
 /lib64/libc.so.6(abort+0x17b) [0x7f06c6cc125b]
 /usr/bin/mongod(_ZN5mongo13fassertFailedEi+0xde) [0xd99e9e]
 /usr/bin/mongod(_ZN5mongo7replset14multiSyncApplyERKSt6vectorINS_7BSONObjESaIS2_EEPNS0_8SyncTailE+0x12c) [0xc2342c]
 /usr/bin/mongod(_ZN5mongo10threadpool6Worker4loopEv+0x281) [0xda7971]
 /usr/bin/mongod() [0xe225d9]
 /lib64/libpthread.so.0(+0x7c6b) [0x7f06c79c7c6b]
 /lib64/libc.so.6(clone+0x6d) [0x7f06c6d6d5ed]

My understanding is that a duplicate key error shouldn't cause a fatal crash.
I looked in Jira but didn't find an exact match for this issue.
Is this a known mongodb problem? 

Thanks
Sergey Novgorodsky