Looks like the file is corrupt or the underlying file-system might be having problems.
I'm not sure if your distro checks the file system every time it boots (probably not, it is done periodically). The following command forces a file-system check on the next (re)boot (as root user): touch /forcefsck
Reboot your machine.
If all went well your file-system will be checked and (hopefully) automatically repaired.
If the /forcefsck file is still present after you boot, remove it (as root): rm /forcefsck
Hope this helps.