I'm having a problem that I can easily reproduce. The problem started today. I did a clean install of 10.9.2 and FCPX 10.1.1, Motion, and Compressor. I also installed the most recent version of the Promise Utility and updated the firmware to the newest version on my Pegasus R4. I've been experiencing terrible performance on a late 2012 27" iMac with 32GB ram. That's another issue though.
I have 2 FCPX stations. The first is the iMac. The second is a retina Macbook Pro. All the media and libraries are stored on the Pegasus connected to the iMac. When an editor works on the MBP we use file sharing to mount the Pegasus volume over gigabit, and copy the Library over to local storage. Edit with the linked media over the network, and when we get done we copy the Library back over to the Pegasus and replace the original. It's been working well for a while. We did the same thing with Projects and Events before 10.1.
After the clean install and updates we are having a major issue. When we copy the Library back to the iMac we get an error that the Library can't be replaced (or Deleted when we try that), because Original Media is in use. There is nothing open on the iMac. We have tried restarting, going back to older firmware on the Pegasus. Same results every time.
The terrible part is that after this "Original Media is in Use" error all of the (linked) actual media files located on the Pegasus are gone. It's like they never existed. Not in the recycle bin. Nothing. All of the alias files are still inside the original media folder in the library package, but if you open the Library again in FCPX everything is offline and the media is nowhere to be found.
I do wonder if this could have something to do with Library Manager -something I added recently, and can't say we worked by copying a library back and forth since I downloaded it. It isn't open, but could it be holding onto the Original Media folders for it's feature that checks to make sure that media is present before deleting generated files? Does it somehow run in the background?
Here is an update in case anyone else runs into this. Upgrading to Mavericks from a previous version of OSX it seems, at least on my systems, left SMB file sharing disabled. When I did the clean install of Mavericks both SMB and AFP were enabled under the options in the file sharing preferences. I remember reading that apple is moving toward SMB2 (with mavericks?) but there must be a few glitches. I think the first two Mavericks updates addressed issues with SMB or file sharing.
Anyway, I disabled SMB on the iMac and no more issue.