I am running a single mongodb server in CentOS v6.5 64bit.
One day, the server was down due to power's problem.
After server's restarting, there has been a problem with mongodb's gridfs.
Some files cannot be read, and repair cannot work. At that time, the mongo version wat v2.4.3.
I thought it wat old version's bug, so I upgraded the version to v2.6.10.
But the problem is still.

I store many small files is gridfs, with gridfs's id to access the file, such as:
http://xxxx/media/557e84883e2ff5522200001f/file.jpg

How can I fix this problem? And ensure the old files id not be changed.

Assertion: 10334:BSONObj size: 0 (0x0) is invalid. Size must be between 0 and 16793600(16MB) First element: EOO