It'd be nice to get rid of the stack trace here.

Wed Mar 9 21:11:18 [conn13] Assertion: 10412:moveAndCommit failed: { who: { _id: "docs.spreadsheets", process: "ip-10-203-75-200:1299691738:429763674", state: 1, ts: ObjectId('4d77ecf62af705546abfddcd'), when: new Date(1299705078458), who: "ip-10-203-75-200:1299691738:429763674:conn37:932882091", why: "migrate-

{ username: "abbott", _id: ObjectId('4d77daaf9ba57d22cd00461a') }

" }, errmsg: "The collection's metadata lock is already taken.", ok: 0.0 }
0x5255e9 0x627afc 0x62a3ae 0x648656 0x64ade0 0x6767b2 0x689821 0x58ecc2 0x6b0db0 0x319ca07761 0x319bee0e7d
mongos(_ZN5mongo11msgassertedEiPKc+0x129) [0x5255e9]
mongos(_ZN5mongo5Chunk12moveIfShouldEN5boost10shared_ptrIS0_EE+0x5bc) [0x627afc]
mongos(_ZN5mongo5Chunk13splitIfShouldEl+0x31e) [0x62a3ae]
mongos(_ZN5mongo13ShardStrategy7_insertERNS_7RequestERNS_9DbMessageEN5boost10shared_ptrINS_12ChunkManagerEEE+0x686) [0x648656]
mongos(_ZN5mongo13ShardStrategy7writeOpEiRNS_7RequestE+0x260) [0x64ade0]
mongos(_ZN5mongo7Request7processEi+0x172) [0x6767b2]
mongos(_ZN5mongo21ShardedMessageHandler7processERNS_7MessageEPNS_21AbstractMessagingPortE+0x141) [0x689821]
mongos(_ZN5mongo3pms9threadRunEPNS_13MessagingPortE+0x272) [0x58ecc2]
mongos(thread_proxy+0x80) [0x6b0db0]
/lib64/libpthread.so.0() [0x319ca07761]
/lib64/libc.so.6(clone+0x6d) [0x319bee0e7d]