the only way that i have come across to fix this problem is to boot from another mac osx partition or the instalation CD/USB and go to the disk utility and then click on the hard drive in question and then push the "repair disk" button , this takes about 4-5 hours but seems to do the job , hope this helps
I now have this problem on two different 10.8 servers. They are under warranty, so I called support. We have been through hards drives and they were suggesting logic board. I didn't want to do that and then it started on the second server (xserver this time, the first one is a Mac Pro) Obviously this is an error with the OS. I have run repairs from various tools and it comes back. Tried copying off files etc, nothing works. I would like to hear from an engineer on this - does anyone from Apple look at the commumities support?
Logically as it is complaining about drive C an external drive, it should be possible to repair it either on another computer, or even on the server itself. A possible reason you cannot repair it on the server itself is if it is being used by the server software e.g. is being shared via AFP. However as another Mac says it is fine this is indeed puzzling.
I can however suggest another approach which might help.
Boot your server in safe mode by holding down Command-S
It should boot in to a text only environment known as 'single-user mode'
Then when you get the command prompt, type /sbin/fsck -fy and press return
I find that firstly the process of booting in to single-user modem can help with 'replaying' journals but in single-user mode the drives are also not going to be in use and fsck is the same underlying tool that Disk Utility uses.