In Keynote '13, A dialog box keeps giving me a warning when I save / autosave

The following warning appears:

This happens both when I save and the autosave (which happens often). It is a modal box and interrupts workflow.

No other applications are running, and the issue survives program and operating system restarts. What could be causing this?

(This issue is new with Mavericks / Keynote '13).

The file might be being modified by another process. You can see as the file is accessed by various processes by running:

sudo opensnoop -f /path/to/file

Use the file normally, then attempt to save. If you get the error, check back in Terminal to see if any other processes have accessed the file.

Use the fs_usage (man page) command to monitor, in real time, accesses to your Keynote presentation.

1. Open Terminal (or iTerm, et al).

2. Copy/paste the following into your Terminal window, replacing the word FILE with the filename of your Keynote presentation (keep quotes if your filename contains spaces or other non-ASCII characters):

   sudo fs_usage | egrep "FILE" # e.g. "My Preso.key"

3. Open your Keynote presentation. In your Terminal screen, you'll see a bunch of output related to opening the file this like so:

    11:29:55  getattrlist       /path/to/My Preso.key           0.000003   Keynote.app   
    11:29:55  getattrlist       /path/to/My Preso.key           0.000005   Keynote.app   
    11:29:55  getattrlist       /path/to/My Preso.key           0.000005   Keynote.app   
    11:29:55  lstat64           /path/to/My Preso.key           0.000002   Keynote.app   
    11:29:55  getattrlist       /path/to/My Preso.key           0.000012   Keynote.app   
    11:29:55  getattrlist       /path/to/My Preso.key           0.000012   Keynote.app   
    11:29:55  lstat64           /path/to/My Preso.key           0.000006   Keynote.app   
    11:29:55  access            /path/to/My Preso.key           0.000013   Keynote.app   
    11:29:55  open              /path/to/My Preso.key           0.000016   Keynote.app   
    11:29:55  open              /path/to/My Preso.key           0.000007   Keynote.app

Then, do what you normally do in your spreadsheet. You may want to align your windows so you can see your Terminal window while you work. Whenever there's new output in your Terminal window, check the last column. It should normally say Keynote.app but if there's an access by any other process, you'll see it there and then you'll have your culprit.

My thinking is that this is a permissions problem or a server problem.

Do you have any servers mounted?

If you save a file to your Documents folder does the problem occur?

Have you tried deleting and reinstalling Keynote?

Are you "sharing" the document so that Keynote has put it in your iCloud account?

Have you tried running Disk Utility and got it to verify permissions on your drive?

If you are having a permissions problem then I'd have a close look at ~/Library/Saved Application State/com.apple.iWork.Keynote.savedState and it's contents as well as any server you have mounted.