mount: unknown filesystem type 'ext3'

mount: unknown filesystem type 'ext3'
  
I use CentOS   6.4, 64 Bit. Today I tried to mount my ext3 partition.Suddenly I was unable to mount my ext3 drives.

When  I tried to mount ext3 file systems, I got the following error.

mount: unknown filesystem type 'ext3'

I tried inserting ext3 kernel module.
 
insmod /lib/modules/2.6.32-358.el6.x86_64/kernel/fs/ext3/ext3.ko 

When I issued this command, I got this error,

FATAL: Error inserting ext3 (/lib/modules/2.6.32-358.el6.x86_64/kernel/fs/ext3/ext3.ko): Unknown symbol in module, or unknown parameter (see dmesg)

I traced by issuing,

dmesg

which showed,

ext3: Unknown symbol journal_force_commit

By searching for this error, I came to this page,

http://www.dd-wrt.com/phpBB2/viewtopic.php?p=547719

In that page, they suggested to try the following


Code: 

insmod mbcache
insmod jbd
insmod ext3  

So, I tried ,

locate mbcache
insmod  /lib/modules/2.6.32-358.el6.x86_64/kernel/fs/mbcache.ko

locate jbd.ko
insmod /lib/modules/2.6.32-358.el6.x86_64/kernel/fs/jbd/jbd.ko


insmod /lib/modules/2.6.32-358.el6.x86_64/kernel/fs/ext3/ext3.ko
modprobe jbd
modprobe ext3

At last these steps solved the error.
I wonder why suddenly the modules get unloaded on reboot ?