Did the drive loose connectivity? Is the drive full? Maybe permissions error? Did you restart the server and try it again and get the same error?
I have had similar issues when trying to upload a large file to FMS 13. In my case the server is my development box, a new Mac Mini. I found that when this happened, stopping FMS and then rebooting the server seemed to resolve it. In my case this is easy to do since I'm the only user. For a production box a full restart like this can be more problematic.