standalone mongod with journaling was turned off, and restarted with automatic recovery.
but when using mongoexport, it splits out the assertion 10320 and can't have the job done successfully.

Wed Aug 29 14:41:24 Assertion: 10320:BSONElement: bad type -100
0x581222 0x50464b 0x513249 0xaa3c0f 0xa9ca9d 0xaa0702 0x3598a1d994 0x4fe4f9
/home/mongodb-linux-x86_64-2.0.7/bin/mongoexport(_ZN5mongo11msgassertedEiPKc+0x112) [0x581222]
/home/mongodb-linux-x86_64-2.0.7/bin/mongoexport(_ZNK5mongo11BSONElement4sizeEv+0x1cb) [0x50464b]
/home/mongodb-linux-x86_64-2.0.7/bin/mongoexport(_ZNK5mongo7BSONObj10jsonStringENS_16JsonStringFormatEi+0x1d9) [0x513249]
/home/mongodb-linux-x86_64-2.0.7/bin/mongoexport(_ZN6Export3runEv+0x11bf) [0xaa3c0f]
/home/mongodb-linux-x86_64-2.0.7/bin/mongoexport(_ZN5mongo4Tool4mainEiPPc+0x169d) [0xa9ca9d]
/home/mongodb-linux-x86_64-2.0.7/bin/mongoexport(main+0x32) [0xaa0702]
/lib64/libc.so.6(__libc_start_main+0xf4) [0x3598a1d994]
/home/mongodb-linux-x86_64-2.0.7/bin/mongoexport(__gxx_personality_v0+0x3c9) [0x4fe4f9]
assertion: 10320 BSONElement: bad type -100

I did repair database, and solved that problem.