EXT3-fs error - Freeing blocks not in datazone

[samix_119 yahoo com]

Hello,

* One of our servers experienced a file system corruption and gave this error in the /var/log/messages file.

{code}
Jun 17 05:53:47 myhost kernel: EXT3-fs error (device sdb1): ext3_free_blocks: Freeing blocks not in datazone - blo
ck = 2684399216, count = 1
Jun 17 05:53:47 myhost kernel: Aborting journal on device sdb1.
Jun 17 05:53:47 myhost kernel: EXT3-fs error (device sdb1) in ext3_free_blocks_sb: Journal has aborted
Jun 17 05:53:47 myhost kernel: EXT3-fs error (device sdb1) in ext3_free_blocks_sb: Journal has aborted
Jun 17 05:53:47 myhost kernel: EXT3-fs error (device sdb1) in ext3_reserve_inode_write: Journal has aborted
Jun 17 05:53:47 myhost kernel: EXT3-fs error (device sdb1) in ext3_truncate: Journal has aborted
Jun 17 05:53:47 myhost kernel: EXT3-fs error (device sdb1) in ext3_reserve_inode_write: Journal has aborted
Jun 17 05:53:47 myhost kernel: EXT3-fs error (device sdb1) in ext3_orphan_del: Journal has aborted
Jun 17 05:53:47 myhost kernel: EXT3-fs error (device sdb1) in ext3_reserve_inode_write: Journal has aborted
Jun 17 05:53:47 myhost kernel: ext3_abort called.
Jun 17 05:53:47 myhost kernel: EXT3-fs error (device sdb1): ext3_journal_start_sb: Detected aborted journal
Jun 17 05:53:47 myhost kernel: Remounting filesystem read-only
Jun 17 05:53:47 myhost kernel: __journal_remove_journal_head: freeing b_committed_data
{code}

* The file system then went into read only mode

* We tried to unmount and then remount the file system,but on trying to unmount the server simply hung and we had to restart the machine

* Fsck found errors on the file system and fixed it

* This filesystem is on a raid partition (RAID 1) and the physical and virtual disk caches are turned on.

* Even the barrier option for this file system was on to prevent any corruption of the data in case of a sudden reset

* Can some one please point to me what is that went wrong exactly and how we can avoid this in the future

Regards,
Muhammed Sameer